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Blog - engineering

Datalogger Discovery Newsletter July 26, 2016

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Graphtec dataloggers have long been regarded as the go-to multichannel, portable datalogger for 10 channel and above applications for recording temperature and voltages signals. In this issue of our discovery newsletters, we explore the engineering scaling feature more in depth as we cover the details on how signals from pressure transducers, flow meters, LVDT displacement sensors and various other signals are used in conjunction with the Graphtec GL series.

Also, discover how additional testing can be made with various physical parameters like distance, pressure, flow, and speed.

wlan wireless dataloggers



standalone screen based dataloggers

Multiple sensor manufacturers in the industrial, research and development fields provide output signals that are scaled in voltage DC signals or 4 to 20mA current loops. Graphtec dataloggers are able to scale these signals to its original unit of measurement and record data in their respective scales such as pressure (PSI), length (feet), area, frequency (RPM), energy (W) and flow (gal/s).

datalogging with engineering scaling

The Engineering Unit (EU) setting available on the GL240, GL840s, GL900, and the GL7000 are a direct ratio mapping feature where you set the minimum and the maximum input values from the input signal, and output the EU values in terms of the unit of measurement proportional to that range.

voltage and temperature engineering scaling input

4 to 20 mA current ShuntIn industrial applications, 4 to 20 mA current loop signals dominate the output conversion of the pressure and flow signals. Graphtec is able to take these signals--using the model B-551 250ohm shunt resistor (pictured). Using the B-551 shunt, 4-20mA converts to a 1-5VDC signal as the signal enters the input channels on the GL series. Thereafter, the 1-5VDC can be scaled to its original unit of measurement using the max and the min values for the output signal. Here is an example of the measurement value and EU value for a pressure transducer that scales up to 10,000 PSI using a shunt resistor for a 4-20mA current loop signal.

Default Measurement Units for Metric Units and Custom Key configurations for Imperial Units

    There are now 15 categories available as default measurement units on the scaling feature. All of the default units are in metric, but you are also able to key in the imperial units like inches, pounds, and even PSI in text annotation. Here are all the default measurements available on the Graphtec GL dataloggers:

Default Measurements dataloggers


Speed, Flow Levels, and Totalization

Tachometer and flow sensors that provide pulse signals for rate and speed of flow can be measured and scaled using the GL series line-up with B-513 logic/pulse cable. Four channels are available for pulse signals in this configuration. “Engineering Unit Setting” is also available for all four channels. When monitoring speed rates from a tachometer or an IR speed sensor, pulse signals can be scaled from the measurement value of sensors available in each rotation to an RPM as shown below.

datalogger engineer scaling flow sample


datalogger engineering unit setting

blue bullet For flow signals, the individual pulse signal can be converted to the equivalent flow rate as shown above.

Totalization of flow rates are provided in total gallon in terms of volume. This can be calculated using the “Instantaneous Count” feature where every pulse signal per sampling rate is chosen (ie. 10 pulse signal per 1 minute interval) and will give you the total volume received under the particular sampling interval (in this case a one minute interval).


Please consult the Graphtec Technical Sales and Support teams at inst.support@graphtecamerica.com & at inst.sales@graphtecamerica.com to discuss your specific applications.

graphtec datalogger screen based



Ability to record signals for temperature, voltage, pressure, length, displacement, flow, and many other variables available through sensors that output direct proportionate linear and analog VDC signals.


Works with your flow signal both in terms of rate and volume, and records all data in real time.


By using model B-551 250 ohm shunt resistor, you are able to record any 4 to 20mA current loops available in most industrial testing solutions.


Product Fact Sheet

Engineering Scaling Feature

  • 4-20mA Current Loop Recording using B-551 250ohm Shunt Resistor
  • EU Scaling for direct y=mx+b scaling
  • Map the scales with min/max input and output values
  • Totalization Available for Flow Signals for volume measurement
  • Pulse signal scaling available for Speed, Flow signals
EU Scaling basic specs chart