Measuring and testing

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Rate this link Simple method tests cables - Engineers have long known how to test a cable for continuity by simply connecting all conductors in series and checking with an ohmmeter. Some cable TV system measurements use a wideband noise source as the transmitter and a spectrum analyzer as the receiver difference on the signal spectrum on the transmitting and receiving ends tells the attenuation on different frequencies. However if so, please still offer the original rectangular bags. About This Item We aim to show you accurate product information. The megger consists of a hand-driven DC generator and a direct reading ohm meter. I bought these bags originally to carry extra meds in my purse much more convenient than carrying the whole bottle. However, the level of RF voltage being measured provides useful information only when the probe has been designed for use with a specific multi meter.

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However, one must watch out as what is really being measured and exactly what the counter is "seeing". General information Frequency Counter Measurement Techniques - Inexpensive frequency counters that will measure frequency well into the microwave range are available to the hobbyist today. Rate this link Frequency counter circuits Fr? Rate this link Prescaler circuits Prescalers are circuit which are used to extend the meausrement range of other frequency measuring circuits.

If you have for example a frequency coutner which can count up 10 Mhz, then with suitable prescaler circuit you can extend the measurement range to higher frequencies. For example suitable 1: And prescaler with higher division factor will enable you to measure even higher frequencies. The input resistance varies from down to 30 Ohms, and the input capacitance, excluding the PCB, no more than 5pF.

Frequency to voltage converters are not usually as accurate as real frequency counter circuits, but they are still useful in many applications. Rate this link Idea for a car tachometer - A tachometer is simply a means of counting the engine revolutions of an automobile engine.

In this suggested idea a NE timer is configured as a monostable or one shot. The timer receives trigger pulses from the distributor points. Integration of the variable duty cycle by the meter movement produces a visible indication of the automobiles engine speed. Rate this link Pulse period to voltage converter - This circuit converts a square wave input signal into a voltage proportional to the time between edges period of the signal, not the frequency, the range is from uS to to 10mS, which produces a voltage from mV to 10 volts.

A functional feature, retriggering, of a monostable, one-shot 74xx multivibrator can yield frequency discrimination. This circuit is a frequency discriminator that determines the relation of input-pulse frequency to a reference frequency.

It tells if the input frequency is above or below the reference frequency. Rate this link Time measurements Got the Time? Rate this link Time-tag impulses with zero-crossing circuit - A "constant-fraction discriminator" usually performs the time-tagging of impulsive events, which have a peaking time of the signal amplitude. Rate this link Audio measurements Audio volume is the most commonly measured audio signal property.

VU and dB meters both measure the audio power involved in recording and they both use logarithmic scales to report that power. When measuring electrical signals the following is true: VU is short for "volume units" and it is a measure of average audio power. A VU meter responds relatively slowly and considers the sound volume over a period of time.

A dB meter responds very rapidly and considers the audio power at each instant. When measuring electrical signals decibel is the difference or ratio between two signal levels; used to describe the effect of system devices on signal strength. A signal strength or power level; 0 dBm is defined as 1 mW milliWatt of power into a terminating load. When measuring audio signal power vibrations in air the following measurements are made: The decibel abbreviated dB is the unit used to measure the intensity of a sound.

On the decibel scale, the smallest audible sound near total silence is 0 dB. A sound 10 times more powerful is 10 dB. A sound times more powerful than near total silence is 20 dB. What does 0 dB mean? This level occurs when the measured intensity is equal to the reference level. In this case we have equation: Most typically harmonic distortion needs to be measured.

Harmonic distortion describes a nonlinear property of systemswhere the output of the system has added energy at frequenciesthat are at integer multiples of the frequencies input to thesystem. The traditional technique is to input a single frequency F into the system under test, then take the output, apply a filter thateliminates F, and measure everything that's left over.

This is usually done with a twin-T, high-G notch filter centered on F. Nowadays computer techniques can be applied where a more detailed analysis can be made usually based on FFT methods where harmonic and non-harmonic componentscan be identified.

Measuring audio music voltages on an AC voltmeter will give meaninglessresults as the voltmeter measures the average, over a fairly longintegrating time. This means that the level indicated will depend totally onthe programme content of the CD being played. Most multimeters are designed for AC power line work and DC measurements, so perfomance up to Hz or little bit over it is enough.

To make any meaningful measurement, you need to us a CD with single frequency tones, and, unless you know that the meter measures well at higher frequencies, keep to a low frequency, ideally 50Hz, but generally up to acouple of hundred Hz will be OK. Some of the "RMS" digital units might be useful ifthe frequency response is extended and flat enough. The multimeters vary in performance, so it is worth to check their performance on this even some cheap ones can perform accpetably on audio frequencies if a very good absolute accuracy is not needed.

It produces fantastic displays on three LED bars that can be individually adjusted for any particular frequency range. Double-blind and ABX tests do not allow the listener to know which component they are listening to, and furthermore don't allow the test controller to know either. This guards against visual cues to the audience including body language. This feature is adequate to prevent clipping but does a poor job of reading the average volume, or loudness, level.

A high-resolution, average- not peak- reading volume-unit meter produces an accurate reading of loudness. The design is unique in that it detects both stereo channels on a single peak-hold capacitor. All the adjustments in the circuit simultaneously apply to both left and right stereo inputs. The output is suitable for driving a bar-graph display or for analog-to-digital conversion and display with a microprocessor. The circuit operates as a dual positive-peak-detector circuit. If you do you will need a good signal tracer, a device capable of amplifing minute amounts of audio to a point where they can be "read out" on a pair of monitoring headphones.

Such a gadget is shown in the accompanying schematic. These components may develop excessive signal attenuation and losses, or poor isolation between inputs and outputs. These components can be tested using a RF signal source, termination resistors, and the Frequency Selective Voltmeter.

Rate this link Power and field strength meters A field strength meter is perhaps the simplest piece of RF test equipment that can be built. Used for checking transmitters, antenna experimentation, and testing RF oscillators, field strength meters provide an indication of the presence of RF energy. They are generally not frequency sensitive and are useful where indication of a change in level is more important than the actual strength of the signal indicated.

The meter works by converting any RF signal present at the antenna to a DC voltage. This voltage drives a meter movement to give an indication of relative RF.

Usually the meter includes a control to reduce its sensitivity where required. An RF field monitor - This is the oddest application of a neon glow lamp, that is used as a electromagnetic field detector.

In fact the trigger voltage of these lamps is a little bit lower in presence of a strong field. A UJT transistor and a transformer a common low power AC transformer are used to produce a high voltage of about Vac. This voltage is reduced by the trimmer to a value just below the trigger voltage of the lamp.

In presence of a strong field the trigger voltage drops and the lamp lights. Rate this link 2. Beloq 1 GHz this proe has very flat response. This is an useful tool for RF interference troubleshooting! For EMC investigations, you can also clip this meter on to coaxial cables, rotator cables and other wiring in your shack, to find out where the RF currents are flowing, and how big they are. Rate this link Designing RF Probes - An RF probe is used to directly measure the level of RF voltage present at a particular point and is one of the most useful test instrument in the hands of the home brewer.

It is normally used with a digital multi meter to indicate the voltage level as dc voltage which is equivalent to the RMS value of the RF voltage being measured. However, the level of RF voltage being measured provides useful information only when the probe has been designed for use with a specific multi meter. The design of the RF probe is a function of the DC input resistance of the meter we intend to use with it. If a new meter with a different input resistance is used with the probe the reading will be inaccurate.

Rate this link Field-Strength Meter - Simple circuit based on old issue of "73 Radio Electronics", changed a few components to get better sensitivity. Rate this link Field Strength Meter - This RF field strength meter use only few parts, a printed circuit board is not necessary; components can simply be soldered to one another. Rate this link Field-Strength Meter I - This circuit is a electromagnetic field meter which can be used for meaturing of transmitters output power.

Rate this link Field-Strength Meter II - This circuit is an electromagnetic field meter which can be used for meaturing of transmitters output power. Rate this link Funky Fresh? This circuit uses the AD, a high-frequency true-power detector. Using only 3 electronic components, it may rank as one of the simplest and cheapest homebrew projects.

When used with a high-impedance DC Voltmeter, it can be used to measure RF voltage and power , trace RF signals in a new design, and troubleshoot malfunctioning RF circuits. The voltage shown will not be accurate, since this is a rectifier probe, but the measurements are good enough for you to be able to determine where the RF stops, or if a stage is not giving the gain you think it should.

The unit is cheap and fairly basic, but perfectly adequate for its intended purpose. However, the output is not a pure sine wave. The unit covers a frequency range of KHz to 12MHz over five ranges shown below. It may also be used for RF alignment of SW circuits from 25 to 49 metres. The output may be amplitude modulated by an internal Hz audio tone approx. The output level is adjustable in two ranges up to a maximum of about 4V pk-pk.

The unit is mains powered V AC. Rate this link Impedance measurements Couplers Couplers are passive devices used in cable systems to divide and combine radio frequency signals. Many RF systems use directional test points and non directional test points. Directional coupler separate inbound and outbound signals separately. A non-directional coupler allows the measuring technician to see both forward and reverse signals at the same time sum of them. This situation allows only one test point to be used for forward and reverse, but there is potential possibility for measuring errors due to reflections from the bad cable or passive.

Reflections can add or subtract to the actual levels. The non directional coupler is a device presenting a fairly high impedance to the circuit being measured, minimizing the loading effects. Non-directional couplers are generally implemented as high impedance towards the line resistive attenuation taps wired to the line. They typically have quite high attenuation dB typical. Directional coupler is a transmission coupling device for separately sampling through a known coupling loss either the forward incident or the backward reflected wave in a transmission line.

A directional coupler may be used to sample either a forward or backward wave in a transmission line. A unidirectional coupler has available terminals or connections for sampling only one direction of transmission; a bidirectional coupler has available terminals for sampling both directions. Directional couplers are used in a wide variety of applications and can satisfy almost any requirement for sampling incident and reflected RF or microwave power conveniently and accurately with minimal disturbance to the transmission line.

Some general applications for directional couplers include line monitoring, power measurements and load source isolators. A directional coupler has at least three ports: The signal passes between line in and line out ports with loss referred to as the insertion loss.

A small portion of the signal power applied to the line in port passes to the tap port. A signal applied to the tap port is passed to the line in port less the tap attenuation value. The tap signals are isolated from the line out port to prevent reflections. A signal applied to the line out port passes to the line in port and is isolated from the tap port. Building a Non Directional bi directional Coupler - A non directional coupler sees forward and reflected power at the same time, from either direction.

A non directional coupler can be built from a common drop splitter or directional coupler. The tap output is attenuated by 30 dB. Rate this link Directional Coupler Those coupled lines are used to construct directional couplers. Generally, in design of directional couplers microstrip and stripline forms are used. There are many kinds of directional couplers in different forms. The best theoretical performance available from a directional coupler, using ideal transformers, is a function of the turns ratio, and the terminating impedances.

At VHF and UHF frequencies, wire gauge and core material can be chosen to closely approximate the response based on the solution of these equations. The software comes in ascii-text and an X Windows interface using Motif. Signals applied to the input port are sent to the test port and signals coming into the test port can only go to the output port.

The circuit really emulates an isolator in that the actual signal energy is not passed from port to port and the signal levels must be fairly low. The circuit is well suited for testing the SWR of a variety of devices connected to the test port. Rate this link RF spectrum analyzers A mong the many measurement tools sought by the amateur radio experimenter, the most desired - but generally considered the least accessible - is the radio-frequency spectrum analyzer. Spectrum Analyzer is intended for visual inspection of the spectrum of an investigated signal on the oscilloscope screen.

The signal can be continuous or pulsed. Now you can have it - without spending a fortune. A mong the many measurement tools sought by the amateur radio experimenter, the most desired - but generally considered the least accessible - is the radio-frequency spectrum analyzer or SA.

This need not be. Simple and easily duplicated, this homebuilt analyzer is capable of useful measure-ments in the 50 kHz to 70 MHz region. Rate this link Look before you leap: Rate this link Microwave Spectrum Analyzer on a budget - A practical approach to microwave signal analysis for the home experimenter.

The need for standard values can be met by using one or the other. Attenuators with equal terminations have a minimum attenuation of 0 dB. Unequal terminations place a lower limit on the attenuation. A two way matching network uses a Rate this link Radioacivity There are many defices to detect radio active radiation. Geiger counters are devices to detect and measure ionizing radiation, as emitted by radioactive sources. The heart of a geiger counter is the Geiger-Mueller-Tube.

This is a gas filled tube, to which a voltage of several V is applied. Normally, the gas insulates and no current is drawn. When a radiation particle or quantum passes the tube, it triggers a gas discharge, i.

The resulting current impulse can be amplified and made visible or hearable "clicking". Glas mantle tubes are only suitable for beta and gamma rays, as any alphas are absorbed in the glass. Window tubes have a window usually at one end , which is sealed with a very thin foil or mica.

Alphas can penetrate this window, and thus be detected, as well as betas and gammas. There are also diode based radioactive dosage meters in use. Adding heat to a system causes its temperature to rise. While there is no maximum theoretically reachable temperature, there is a minimum temperature, known as absolute zero, at which all molecular motion stops. Temperatures are commonly measured in the Kelvin or Celsius scales, with Fahrenheit still in common use in the Unites States.

There are many ways to measure temperature elecronically. A thermocouple is a very commonly used sensor for measuring temperature. It consists of two dissimilar metals, joined together at one end, which produce a small unique voltage at a given temperature.

This voltage is measured and interpreted by a thermocouple thermometer. In practical applications the so called cold side of the junction is kept close to ambient temperature by bonding it to a temperature stable mass. The hot side of the junction is exposed to the temperature to be measured. Because thermocouples measure in wide temperature ranges and can be relatively rugged, they are very often used in industry.

Thermocouple is a A temperature sensing device made by joining two dissimilar metals. This junction produces an electrical voltage in proportion to the difference in temperature between the hot junction sensing junction and the leadwire connection to the instrument cold junction.

In typical applications the the hot side is in the end of sensor wire and the cold juction in the temperature measurement device near the sensor connector. In many cheap meters this cold junction is just in the same temperature as the meter itself, and it's temperature is measured in other means to compensate the effect of changes in cold junction temperature.

Thermocouple detectors have low impedance. Thermocouples are available in different combinations of metals or calibrations. The four most common calibrations are J, K, T and E.

Each calibration has a different temperature range and environment. Propably the most commonly used type is K-type thermocouple, which is a Ni-Cr-sensor very suiable for degress celsius temteperature measurements can be used from to celsius. The accuracy of any circuit or system that uses a thermocouple to determine the temperature of a process is limited by the accuracy of the method used to perform cold-junction compensation.

In a thermocouple measurement, two wires of dissimilar metal join together at the "hot," or measurement, junction. The isothermal termination of the thermocouple wires provides a second "cold," or reference, junction. The potential across the thermocouple is proportional to the temperature difference between the two junctions. Thus, to determine the absolute temperature of the hot junction, you must also know the absolute temperature of the cold junction.

Resistance Temperature Detector RTD is a sensor that uses the resistance temperature characteristic to measure temperature. There are two basic types of RTDs: A resistive thermal device RTD can measure temperatures as high as ? C over a great distance and without expensive signal conditioning.

The most popular RTD is a standardized platinum temperature sensor called the PT, which exhibits ohms resistance at 0? C and a linear temperature coefficient of 0. C characteristic appears almost linear over a narrow range. A PRTD's transfer function of resistance vs.

C, are approximated by the equation: Unlike thermocouples, which deliver voltages that represent the difference between two temperatures, the resistance of an RTD represents the absolute temperature of that resistance. Measurement is typically accomplished by driving a current of 1mA to 2mA through the sensor and measuring the voltage drop across it.

Also semiconductors can be used as termperature sensors because semiconductor PN junction characteristics change when temperature changes. This change is well defined and this can be used in some temperature measurement applications. The temperature - versus - bulk resistance characteristics of semiconductor materials allow the manufacture of simple temperature sensors using standard silicon semiconductor fabrication equipment. The ordinary semiconductor diode may be used as a temperature sensor because a forward biased voltage across a silicon diode has a temperature coefficient of about 2.

C and is reasonably linear. The forward basing can be done with for example around 1 mA current through the diode. To improve the performance of the diode as a temperature sensor, two diode voltages can be measured with two different currents typically selected to be about 1: The transistor sensor is used in diode mode by connecting the base and collector together or sensor is wired between base and emitter.

Semiconductor temperature sensors are available from a number of manufacturers. There are no generic types. The semiconductor or IC for integrated circuit temperature sensor is an electronic device fabricated in a similar way to other modern electronic semiconductor components such as microprocessors.

C typical , low cost, good accuracy if calibrated but also poor interchangeability. In general, the semiconductor temperature sensor is best suited for embedded applications - that is, for use within equipment. This is because they tend to be electrically and mechanically more delicate than most other temperature sensor types.

The "out of the box" or interchangeability accuracy of most semiconductor temperature sensors is not particularly good. If individual sensors are calibrated, significantly better measurement accuracy is possible tyically a two point calibration or three point calibration is used. Due to the high sensitivity of some sensors, they can be very good in measuring small temperature changes as opposed to absolute measurement.

Bimetallic thermometers are contact temperature sensors found in several forms if you know where to look, e. They typically consist of a strip of bi-metal that has some electrical contacts affixed to it. The temperature changes cause the strip to bend, making or breaking the connection as needed. You will often find long bimetallic strips coiled into spirals. This is the typical layout of a backyard dial thermometer. By coiling a very long strip it becomes much more sensitive to small temperature changes.

In some applications temperature sensing needs to be done without contact to the measured subject. Those measurements use infrared IR techniques. Radiation Thermometers Pyrometers, if you will are non-contact temperature sensors that measure temperature from the amount of thermal electromagnetic radiation received from a spot on the object of measurement. There are two types of commonly used sensors for this kind of applicatons: Pyroelectric Infrared Detectors and Thermopile detectors.

Pyroelectric Infrared Detectors PIR convert the changes in incoming infrared light to electric signals. The pyroelectric detectors output is proportional to rate of change of incident radiation. This means that pyroelectric detectors can only be used to detect temperature changes. This kind of PIR sensors are used for example in movement detectors where they sense the moving hot object like human through special optics this optics makes the movement of hot object change the radiation that gets to sensor change sharply when object moves.

Pyroelectric detectors have very high impedance requiring an internal impedance converting buffer to make them useable. Thermopile detector output is proportional to incident radiation. A thermopile is a number of thermocouples connected in series.

The so called cold side of the junction is kept close to ambient temperature by bonding it to a temperature stable mass. The hot side of the junction is exposed to incident radiation. Some thermopile sensors have a built-in thermistor which provides measurement of the ambient temperature thus allowing the temperature of the target to be calculated.

A thermopile sensor generates a voltage, which is proportional to the incident infrared IR radiation power. Because every object emits IR radiation with a power, which is a strict function of its temperature, one can deduct the object? This method is called pyrometry. Thermopile-type infrared and thermal detectors are used in a number of applications, including infrared spectroscopy, radiometry, security systems, and many consumer products.

Although they do not provide vision-quality images as in the case of quantum detectors, thermopiles are still attractive for many low-cost commercial and industrial applications, mainly because they do not need cooling for operation and the technologies are relativly simple. Thermopile detectors have low impedance. In addition to those some applications use Thermal Infrared imaging camera.

Thermal Infrared imaging camera is a camera that responds to the infrared signals instead of normal light. Thermal infrared imaging cameras are detector and precision optics platforms that give us a visual representation of infrared energy emitted by all objects.

Typical applications for this type of cameras are night vision,wildlife observation, search and rescue, victim location, wild fire recon, predictive maintenance in power transmission and machinery, carona detection, process control and printed Circuit Board evaluation. Depending the applications the IR radiation can be shown as normal grayscale video or through real time color infrared output.

The color conversion converts different radiation intensities to different colors for easy visual inspection of picture. With a well calibrated camera, those different colors on picture can be directly mapped to different temperatures. Thermal infrared imaging cameras are expensive devices bceause they need special imaging sensors that needs to be cooled down to make them operate correctly.

This is the Seebeck Effect, discovered by Thomas Seebeck in The effect is multiplied when there are a number of junctions in series in the circuit, with alternate junctions in close thermal contact with each other. Schematics, mounting instructions and step-by-step instructions included.

Rate this link ECEFast Technical Papers - A selection of temperature measurement information document platinum resistance temperature detectors, thermocouple fundamentals, noncontact thermometers and infrared systems.

Also information on water characteristics measurement conductivity, exygen, pH. This technique is a very good way to detect the temperature of a person's eardrum. Rate this link International Thermocouple Colour Codes: Rate this link Measuring temperatures on computer chips with speed and accuracy-a new approach using silicon sensors and off-chip processing - Silicon sensors are becoming increasingly important transducers in electronic systems. As systems become more complex, more compact, and denser-and run faster and hotter-it becomes increasingly vital to monitor critical temperatures.

Traditional sensor techniques, such as thermocouples, thermistors, and RTDs, are now being displaced by silicon sensors, with their ease of integration and use. Silicon sensors, on the other hand, are linear, accurate, low-cost, and can be integrated on the same IC as amplifiers and any other required processing functions.

The actual sensing element in a silicon sensor is a simple P-N transistor junction. C and this fact may be used to develop a temperature measuring system. Rate this link Omega Technial Reference Section - Lots of technical documents on temperature measurement sensors. Rate this link Pyroelectric detectors - Pyroelectric Infrared Detectors PIR convert the changes in incoming infrared light to electric signals.

Rate this link Remote diodes yield accurate temperature measurements - All of today's PC designs require thermal management. Heat generation is a problem for PC-system designers. To prevent failures, you must incorporate thermal-management features in your design. You can control temperatures by, for example, lowering device voltages and reducing clock rates so that devices generate less heat, or by increasing airflow so that the system can better dissipate heat into its environment.

Because die temperature is a critical parameter, some devices incorporate a means to allow you to measure it. It is aimed at engineer, student, scientist, and technologist alike. Rate this link Temperatures. Rate this link Thermocouples Introduction - The Thermocouple is a thermoelectric temperature sensor which consists of two dissimilar metallic wires, e. These two wires are connected at two different junctions, one for temperature measurement and the other for reference.

Rate this link Track multisite temperatures on your PC - This low-cost circuit allows you to track four remote temperatures with thermistor sensors through the parallel port on your PC. C and a resolution of better than? VBE for a bipolar transistor is a linear function of the absolute Kelvin temperature, T. You can use this truism to make accurate temperature measurements.

The circuit provides analogue voltage output. They are used in a wide variety of temperature measurement and control instrumentation. Rate this link Digital Remote Thermometer - Remote sensor sends data via mains supply, temperature range The Dallas Semiconductor DS digital thermometer allows measurement resolution as fine as 0.

C in digital form and with linear response. The accuracy specification is only 2? C, but you can improve this figure by careful calibration.

Rate this link Qiozl's Temperature Sensor Project - Just a handful of components builds an 8-pin microcontroller based circuit for temperature logging via a serial port; small, fast, and acceptably accurate. But most thermistors' resistance-versus-temperature characteristics are highly nonlinear and need correction for applications that require a linear response.

Using a thermistor as a sensor, the simple circuit presented in this article provides a time period varying linearly with temperature with a nonlinearity error of less than 0. You can use a frequency counter to convert the period into a digital output. Fortunately, several low-cost temperature-sensing integrated circuits ICs are easy to isolate. This application note shows two approaches to isolating temperature sensors. Rate this link Selecting temperature sensors Temperature Sensor ICs Simplify Designs - When you set out to select a temperature sensor, you are no longer limited to either an analog-output or a digital-output device.

There is now a broad selection of sensor types, one of which should match your system's needs. Rate this link Tradeoffs in Selecting IC Temperature Sensors - A discussion of IC temperature sensors has become timely and important because electronic systems are increasingly dense, power-hungry, and hot. Temperature sensors also have a lot of gadget appeal. Many ICs perform highly abstract functions.

Included are seven segment decoders, display drivers, a reference, and a clock. It contains an internal voltage reference, high isolation analog switches, sequential control logic, and the display drivers. The auto-zero adjust ensures zero reading for 0 volts input.

This how this circuit uses that IC to make a voltage meter. Rate this link Digital Volt meter with video output - This design awarded the third international prize in the Elektor Electronics Microprocessor and Microcontrollers Design Contest. Rate this link Circuit yields accurate absolute values - This circuit delivers the absolute value of the input signal with an accuracy better than 10 ppm of the full-scale range.

This technique usually works well unless your design requires operation higher than a few kilohertz. Ships to San Leandro, Davis St. Product highlights No more counting calories Fill the containers for food groups Microwave safe. Simply fill them to perfectly measure meals-fast! No more counting calories or measuring ounces. Eat directly from the containers or combine on a plate for delicious meals. Perfect portions every time! About This Item We aim to show you accurate product information.

Manufacturers, suppliers and others provide what you see here, and we have not verified it. Some good some bad things. Love how they are pretty labeled, but the kids are hard to get off. Gaschie, September 3, For the price these are good however the labels of which items rub off after first wash. Fortunately they are engraved on the bottom of the containers so you can tell which one is for "Protein", or "Veggies".

I have already lost 6 pounds and following the 21 day fix diet plan or you can choose the plan that comes with containers. I needed to lose weight, so I decided to get the perfect portions sizes containers. These containers will control the amount of food I should be eating. So far so good, excellent!

I am having to search all over to try and find them. Please make these are available in all stores! Carla, March 25, I bought these bags originally to carry extra meds in my purse much more convenient than carrying the whole bottle.

Since the opening in on the vertical short side , less likely to spill pills everywhere. My toddler granddaughter has her snacks in her portion bags. But the best use of these bags is for storing precut veggies that I keep in my freezer.

These are ready for quick additions to soup, stew, meatloaf, sauces. Armybear, March 2, As far as for snacks, these are horrible. They are only good for a limited type of items, the opening is very small. I understand that you tried to produce a more specialized bag and the measurement markings is nice. However if so, please still offer the original rectangular bags.

Lily, July 28, The Great Value Portion Pack Snack Bags are a specialty snacking bag that is, by design, made for measuring snacks to be eaten on the go, such as nuts, small crackers, raisins, etc. We are sorry you did not like them. The Great Value Square Snack bags may be a good option for you. They are slightly larger than the rectangular snack bag and are easier to fill and close, especially with larger snack items such as carrots or graham crackers.

Where are my OLD snack bags?!? What in the world was someone thinking when they redesigned the snack bags? The wide opening on the long side has been changed to the small end. Seriously - you have to use a teaspoon to get anything in these.

The old design was perfect for half a sandwich or just a few cherry tomatoes or grapes, but this "improved" design is unusable and impractical. Bring back the wide opening you can actually use. The rectangular snack bags have been replaced with a new square snack bag which is slightly larger and 'square' vs rectangular which is more convenient to fill and holds more of most items.

Give them a try! I love these baggies! They are not intended for small children reaching their hands into them, as one reviewer mistakenly thought--those snack baggies are still available everywhere. These are great for shaking food items out of crackers, etc.

Since they have the measurements on them, you know how much of an item you're putting into the bag without having to count or weigh or premeasure with measuring cups. I had previously purchased them in my local Walmart and was so pleasantly surprised when I opened the box--I just thought I had the regular snack-sized baggies.

These are way better. And you can't buy them online--what???!!!!

Passionate about nutrition and health?