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Connection and Calibration of Strain-Gage Based Transducers Using DI-8B38 Series Amplifiers

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This application note demonstrates the proper connection and calibration of a strain-gage based transducer connected to a DI-8B38 series amplifier.

For this example we'll use a strain-gage based pressure transducer with a 10,000 PSI capacity, an excitation (supply voltage) requirement of 10V and a gage factor (output) of 2mV/V. We'll connect the transducer to a DI-718B housing a DI-8B38-02 amplifier, installed on channel 1.

We'll begin by connecting the positive and negative excitation wires to EX+ and EX- and the positive and negative signal output wires to In+ and In-.

With the transducer connected to the DI-718B and WinDaq up and running, we're almost ready to calibrate to display pressure (PSI). But first we need to calculate a positive full scale (high calibration) value to enter in WinDaq.

To determine the positive full scale value; we'll begin by dividing the gage factor (output) of the transducer by the gage factor (sensitivity) of the amplifier. This gives us the gain ratio (R). In this case:

Next, we’ll divide the full scale measurement range of the transducer (10,000 PSI) by R to yield the positive full scale (high calibration) value:

Now that we know the positive full scale value, we can use Low and High Calibration in WinDaq to display engineering units (PSI). Use the DI-8B38 Strain-Gage Positive Full Scale (High Calibration) Value Calculator to determine the Positive Full Scale Value you should use in your application.

We'll begin by selecting 'Low Calibration' from the 'Edit' pull-down menu.

Since our transducer outputs 0V at rest; we'll enter 0 (zero) for Input Level and 0 (zero) for Low Cal Value.* For Engr. Units enter PSI.

Next we'll choose 'High Calibration from 'Edit' pull-down menu.

We'll enter 5 Volts for Input Level and 15,000 for High Cal Value.

Finally, to display the actual measurement range of the transducer; we'll select 'Limits' from the 'Scaling' pull down menu. Enter 10000 for the Top Limit and 0 for the Bottom Limit.

That's all there is to it! Channel 1 now displays PSI over the full scale range of the transducer.

*Unbalanced transducers (those with a voltage offset at calibrated zero) may be forced to zero by leaving the offset value in the Input Level field unchanged and entering 0 for Low Cal Value.

See Also How To Calibrate Strain Gage-Based Transducers Using DI-5B38 Strain Amplifiers