Pico Technology

Acceleration

Pico products for measuring acceleration
The most popular product for measuring acceleration is the ADC212 pc based oscilloscope. Most moving coil and piezo sensors (see below) can be plugged directly into the ADC212. Silicon sensors are often '10V bridge' type sensors that require a 10V excitation voltage and produce a millivolt output. An additional precision 10V power supply will be required when using Silicon sensors with Pico products.

Other Information
There are several types of accelerometer:

• piezo-resistor
• piezo-electric
• silicon bridge
• micro machined silicon
• voice-coil

Piezo resistor
A piezo-resistor sensor uses a piece of material whose resistance changes when it is compressed. When the weight is accelerated, it exerts a force on the piezo-resistor. If a constant current is passed through the piezo-resistor, the voltage changes. Current is about 4-8mA and voltage is 8-24V. Typical sensitivity is about 100mV/g over the range 0 to 50G. This type of sensor is available up to 10kHz.

Piezo electric
A piezo-electric sensor generates charge when it is accelerated- typically 50pC per G. It is necessary to integrate the charge to give a voltage which is related to the acceleration: this means that it is not suitable for low-frequency work, however piezo-electric sensors are available up to 30kHz.

Silicon Bridge
A silicon bridge sensor is a piece of silicon that has been etched to leave a block of silicon at the end of a beam. When subjected to acceleration, the block exerts a force on the beam and the resistance of the beam changes. Maximum frequency is about 5kHz. The sensor is a bridge, and so it requires an excitation signal of 5-10V. Temperature compensation is required.

Micro machined silicon
Micro machined silicon accelerometers are based on a differential capacitor approach. One of the advantages of this type of sensor is the ability to measure DC acceleration (and consequently tilt). The maximum frequency is about 1kHz. The popular Analog Devices ADXLxxx range of single and dual axis sensors have built in signal conditioning circuits that produce a voltage output suitable for use with our data loggers and oscilloscopes.

Voice coil
Voice coils work on the same principle as a microphone, hence the name.

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Audio Signals

Pico products for measuring audio signals
For measuring high end audio signals and for audio spectrum analysis the ADC216 is ideal. For less demanding applications the lower cost ADC212 can also be considered.

Other Information
The Pico THD program can be used to automate common audio measurements such as THD, SINAD and SFDR. It can be downloaded free of charge.

We also have the following application notes on audio measurement:

• Audio Spectrum Analysis: Introduction and testing a CD player
• Audio Spectrum Analysis: Testing power amplifiers
• Audio Spectrum Analysis: Designing audio amplifiers using spectrum analysis
• High Resolution Oscilloscopes

Automotive Signals

Please visit our automotive diagnostics site for more information.

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Battery Discharge

Pico products for measuring battery discharge
Pico has several products suitable for recording battery discharge.

The ADC11 has 11 analogue input channels. The input voltage range is 0 to 2.5V and the resolution is approximately 2.5mV. This device is suitable for measuring multiple channels at higher speed. It connects to the PC via a printer port.

The ADC22 has 22 analogue input channels. The input voltage range is 0 to 2.5V and the resolution is approximately 2.5mV. It connects to the PC via a printer port.

The ADC16 has 8 (single ended) or 4 (differential) high resolution analogue inputs. The input voltage range is -2.5V to +2.5V and the resolution is approximately 40uV. This device should be used if more precise measurements are required at a slower speed. It connects to the PC via a serial port.

Other Information
Terminal connector boards are available for the ADC11 and ADC16.

We also have the following application note on battery discharge:

• Using an ADC-16 to monitor battery discharge

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Current

Pico products for measuring Current
Pico has several products suitable for measuring and recording current.

The Pico range of current clamps allow current to be measured without having to break into the circuit.

• The PP179 and PP266 current clamps can be used with any of our data logging or oscilloscope products. They can measure AC or DC currents up to 600 A.
• The PP218 and PP264 current clamps can be used with any of our data logging or oscilloscope products. AC or DC current signals can be measured from 10 mA to 60 A.

The Pico Current Monitoring Kit contains current clamps, power monitor, data logger and everything else you need to start logging currents from up to three separate circuits. It is ideal for measuring and balancing 3-phase power supplies as well as machine monitoring and energy efficiency studies.

For relatively small currents a simple shunt resistor can be used to convert the current into a voltage, which the ADC can then measure. This can be done providing the signal can be grounded.

Resistor value can be calculated using the formula below:

Rb=^{V max}/_{I max}

Where Vmax is the maximum input voltage of the ADC, Imax is the maximum measured current and Rb << Rin.

WARNING: This method is NOT suitable for monitoring mains currents. To monitor mains currents, the current clamps should be used with either data acquisition or oscilloscope products.

Pico has two products where this resistor can easily be placed on a terminal board:

• The ADC16 and terminal board - can monitor 8 channels with high accuracy
• The ADC11 and terminal board - can monitor 11 channels at higher speed

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The Beating of a Bird’s Wing

Equipment required:
A high power radar installation (ex military is ideal)
ADC200 PC based oscilloscope
Some birds

This application note looks at tracking migratory birds using radar. Using a PicoScope spectrum analyser it is possible to measure the frequency of the beating of the bird’s wings and from this identify the type of bird.

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Flow

Pico products for measuring flow
There are a wide variety of flow sensors that can be used with Pico products.

Flow is commonly sensed by measuring differential pressure across two points in a pipe. This can be done using the Venturi effect (by placing a restriction in the flow). An alternative approach is to use a Pitot tube. The main advantage of this type of approach is that disturbance of the flow can be kept to a minimum. One disadvantage is that two holes are usually required in the pipe, this can make cleaning difficult, also be aware that many differential pressure sensors are intolerant to aggressive gases and chemicals. The method for measuring these sensors is described in the section on pressure sensors.

For applications where pipes regularly need cleaning, consider using a bending vane type sensor. As the name suggests this consists of a vertical vane that deflects as flow increases. This deflection is measured using a strain gauge. The method for measuring such sensors is covered in the section on strain.

'Paddle wheel' sensors are designed to rotate in proportion to flow. The rotation is detected either by optical or magnetic means. These sensors produce a pulsed output. The main advantage of such sensors is low cost (some are also suitable for measuring aggressive gases and liquids). The main disadvantage is disruption to the flow. For information on interfacing to such sensors see measuring frequency.

Ultrasonic and Magnetic flow sensors allow flow to be measured with no moving parts. This minimises (or eliminates) disturbance to flow and provides for increased reliability. The main disadvantage is cost. These sensors tend to have built in signal conditioning with either voltage or 4 to 20mA current loop outputs.

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Food Temperature Monitoring

Pico products for measuring Food temperature
Pico has several products suitable for monitoring food temperature.

The EnviroMon forms a complete monitoring and recording system than can keep records and plot trends over many years. It is designed as an expandable system for permanent installation in buildings but is flexible enough to be used in many other areas. It is currently being used in large warehouses and supermarkets to monitor food storage conditions and also in factories and houses to monitor a variety of parameters from room temperature to humidity and power usage. Starter kits are available which contain the components required to monitor 3 temperatures, extra components can be added at any later date. The EnviroMon connects to the PC, via a serial port, to download the stored data. It does not require a PC to collect the data.

Several types of sensor can be used with the EnviroMon system:

• Our standard precision thermistor - for ambient and low temperature monitoring
• PT100 RTD - for high temperature monitoring
• Type K Thermocouple - see thermocouple ranges

The TH03 can monitor up to 3 temperatures. It connects to the PC via a serial port and the PC collects the readings directly from the TH03 and up to 9 TH03 units can be used on a PC at once.

The TC08 is our dedicated thermocouple unit. It accepts up to 8 thermocouples using the standard Miniature Thermocouple connectors. It can accept all the standard thermocouple types B, E, J, K, N, R, S and T. The channels can also be used as voltage inputs with a range of +/-60mV. It connects to the PC via a serial port and up to 9 TC08 units can be used on a PC at once.

Other Information
We also have the following application notes available:

• Monitoring temperatures in the food industry - an actual installation
• Monitoring energy efficiency in the home - using EnviroMon
• Advice on choosing and using PT100 sensors
• Advice on choosing and using thermocouples

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Frequency

Pico products for measuring frequency
Many Pico products can be used to measure frequency. The choice of device is dependent on the frequency range, the voltage input range and the number of channels required.

There are three possible measurement requirements:

• Logging frequency variations over time
  • PicoLog can be used to record fluctuations in frequency over time.
• Measuring spot frequencies
  • PicoScope Meter can be used to take spot frequency measurements.
• Investigating the frequency components of a signal
  • PicoScope Spectrum can decompose a signal into its individual frequency component parts allowing the measurement of a particular frequency component within the signal.

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Humidity

Pico products for measuring humidity
Pico has the following products designed for measuring humidity:

The EL026 used with EnviroMon for stand alone data/remote humidity measurement and/or where a number of humidity readings need to be taken over a wide area.

The RH-02 simply plugs into the serial port of a PC and uses internal sensors to give accurate humidity and temperature measurements.

The DrDAQ data logger is a low cost option for humidity measurement using the optional humidity sensor.

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Measuring the Level of a Liquid

This topic is discussed in our science experiment ‘measuring rainfall’

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Measuring Light Levels

Pico products for measuring light

The DrDAQ data logger has a built in light sensor so can be used as a low cost light meter or light level data logger. In addition the light sensor has a fast response time so can be used to investigate rapidly changing light signals such as those produced by tube lights.

The circuit on the right can be used with any of our oscilloscope or data logging products to measure light levels. The circuit uses an LDR to sense the level of light and converts this to a voltage using a potential divider network.

Ra should be around 1M ohm.

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Measuring the Swing of a Pendulum

This topic is covered in the following application note. It makes an ideal physics teaching experiment.

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Measuring pH

Pico products for measuring pH

The DrDAQ data logger has a dedicated pH input. Optional pH electrodes are also available. DrDAQ measures pH over the full 0 to 14 range with a resolution of 0.02pH.

Despite the low cost of DrDAQ, options are provided for calibration and temperature compensation, this allows for very accurate pH measurements.

The circuit on the right allows any of our oscilloscope and data logging products to monitor signals from pH probes . The op-amp needs to have a very high input impedance - an LT1114 is suitable.

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Oxygen in Air

Pico products for measuring oxygen in air

The DD103 oxygen sensor can be connected to the external sensor sockets on the DrDAQ data logger to measure oxygen in air.

Unlike previously available oxygen sensors, the DD103 Oxygen in air sensor can measure the full 0 to 100% range. This makes it ideal for many chemistry, biology and physics experiments.

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Pressure

Pico products for measuring pressure
Most pressure sensors are ‘10V bridge’ type that require a 10V excitation voltage and produce millivolt outputs. An additional precision 10V power supply will be required to provide this excitation voltage when using pressure sensors with any of our products.

• For accurate measurement of up to 4 slowly changing signals use the ADC16 data logger.
• For rapidly changing pressure signals use one of our PC based oscilloscopes such as the ADC212.

Note that some pressure sensors have signal conditioning built in. These sensors usually have a voltage output or a 4-20mA output. See the appropriate sections in this guide for information on measuring these signals.

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Strain, Force and Load

Pico products for measuring Strain, Force and Load
The strain gauge is perhaps the most popular sensor for measuring force and deflection. As a strain gauge is stretched or compressed its resistance changes. By mounting the strain gauge on a calibrated carrier, force can be indirectly measured. Such a sensor is commonly referred to as a load cell. Load cells consist of one or more strain gauges configured in an industry standard ‘10V bridge’ arrangement. Sensitive load cells are used in weighing scales, at the other extreme heavy industrial load cells can be used to measure loads of 1000s of kg.

As mentioned, most load cells are ‘10V bridge’ type that require a 10V excitation voltage and produce millivolt outputs. An additional precision 10V power supply will be required to provide this excitation voltage when using pressure sensors with any of our products.

• For accurate measurement of up to 4 slowly changing signals use the ADC16 data logger.
• For rapidly changing pressure signals use one of our PC based oscilloscopes such as the ADC-212.

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Rainfall

This topic is covered in the following application note

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Radioactivity

The following application note shows how the DrDAQ data logger can be used with a Griffin rate meter to measure radioactivity.

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Resistance

Pico products for measuring resistance
Pico has two products that can be used for measuring and recording resistance.

The PT104 data logger can be used for high accuracy (20ppm) / high resolution (1 µohm) resistance measurement

The DrDAQ data logger can directly measure resistance over the 0 to 1M Ohm range.

Other Information
Other Pico products can also be used to monitor resistance. This is achieved using a precision voltage reference and a known resistance. The two resistances are connected in series and fed by the precision voltage source. The voltage developed across the unknown resistor can then be measured and used to infer the resistance.

Pico has two products where the resistors and voltage source can easily be placed on a terminal board:

• The ADC16 and terminal board - can monitor 8 channels with high accuracy.
• The ADC11 and terminal board - can monitor 11 channels at higher speed.

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Sound Level

Pico products for measuring sound level
The DrDAQ data logger has a built in microphone that can directly measure sound level over the 55 to 100dBA range. Sound level is ‘A-Law’ weighted to approximate the response of the human ear. The low cost of DrDAQ makes it ideal as either a sound level meter or sound level data logger.

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Temperature

Pico products for measuring temperature
Temperature is the most commonly measured ‘real world’ signal. We have several products dedicated to measuring temperature. In addition if you wish to monitor a mix of temperatures and other parameters our data logging products provide a simple ‘plug and play’ solution.

Other Information
We also have the following application notes available:

• Advice on choosing and using thermocouples
• Advice on choosing and using PT100 sensors
• Monitoring temperatures in the food industry
• Environmental monitoring at the olympics

See also:

• Food temperature monitoring

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Video Signals

Pico products for measuring video signals
For measuring video signals consider one of our high speed PC based oscilloscopes. The ADC200/100 and the ADC200/50 are both suitable choices.

Other Information
We also have the following application note on video measurement.

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Voltage

Pico products for measuring voltage
The majority of Pico products can be used for data logging. To ensure you choose the correct product you must consider the following:

• How many voltages (channels) need to be measured
• How big (or small) the voltages are
• How fast the signals change
• How long you wish to record the voltage for

How many voltages (channels) need to be measured?
If your requirement is to measure a large number of channels, then consider the ADC16 (8 channels), the ADC11 (11 channels) or the ADC22 (22 channels). If more channels are required then it is possible to use multiple ADC units on the same PC to give very high channel counts. If you have a number of voltages to record over a wide area, then the EnviroMon networked data logging system can measure up to 30 channels per logger.

How big (or small) the voltages are?
Most of our data logging products have fixed input ranges (2.5V or 5V). These can be easily increased through the use of simple potential divider circuits. Our oscilloscope products have software selectable ranges (10mV to 20V).

If your wish to measure high voltages then the range of our oscilloscope products can be extended to 200V using standard x10 scope probes. For higher voltages (including mains) we recommend the use of one of our oscilloscope products with an isolating x100 differential scope probe.

If you wish to measure small voltages you need to consider the input range of the device and also the resolution:

^* Smallest detectable change

How fast the signals change
If your signals have frequency components in excess of 1kHz then consider our oscilloscope products. If all your signals are lower than 1kHz you can use either our datalogging or oscilloscope products.

How long you wish to record the voltage for
If you wish to record voltages for long periods of time (more than say 5 min), then use one of our PC based data loggers or if you need a stand alone system use the EnviroMon system.

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WBGT (Wet Bulb Globe Temperature)

Pico products for measuring WBGT
WBGT is used to measure the heat load the environment places on humans and other animals. To calculate WBGT it is necessary to measure ambient temperature, humidity and solar radiation. This can be done using the EnviroMon data logger. The equations needed to calculate WBGT are built into the logger. If you have an interest in WBGT measurement please contact Pico technical support for more information.

Other Information
We also have the following application note showing the use of the WBGT index during the Atlanta Olympics.

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4-20mA Signals

Pico products for measuring 4-20mA signals Pico has several products suitable for measuring and recording 4-20mA signals, but the input circuit has to be slightly modified.

A simple shunt resistor can be used to convert the current in the loop to a voltage, which is suitable for the ADC to measure. A 250 Ohm resistor will give a voltage output of 1-5V. This method can be used as long as the signal can be grounded.

Other resistor value can be calculated using the formula below:

Rb=^{V max}/_{I max}

Where Vmax is the maximum input voltage of the ADC, Imax is the maximum measured current and Rb << Rin.

Other Information
Pico has two products where this resistor can easily be placed on a terminal board:

• The ADC16 and terminal board - can monitor 8 channels with high accuracy.
• The ADC11 and terminal board - can monitor 11 channels at higher speed.

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Measuring the Speed of Sound

This topic is covered in the following application note. It makes an ideal physics teaching experiment.

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Measuring the Speed of Light

This topic is covered in the following science experiment. It makes an ideal physics teaching experiment.

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Measuring the Output of a Dynamo

One of our series of educational technical notes, this experiment looks at measuring the output of a bicycle dynamo.

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Measuring the Speed of a Car

One of our series of educational technical notes, this experiment looks at measuring the speed of a car. (Unfortunately due to budget restrictions a rather small car had to be used!)

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Other Measurements

The market is full of different types of sensors, which measure numerous variables and we have been unable to cover them all for this page.

If you have a interface solution for a sensor we haven't listed here, then please e-mail us and we will add it to this page.

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