This Document is not yet Rated

Rate this Document

Measuring the Offset Error of FP-SG-140

Hardware: FieldPoint>>Analog I/O Modules>>FP-SG-140

Problem: I want to calculate the true offset error of my FP-SG-140 module. How can I do that?

Solution: It is very difficult to measure the offset error of a strain gauge module since the module readings can change drastically from just a slight change in resistance. On the other hand, if you build a high precision resistor network, then you can simulate a full bridge strain gauge and calculate the actual offset error. You also need to have a high precision DMM to measure the resistor values to determine the true resistance of the resistors. Assume that we have two 600 Ohm high precision resistors and another 25 Ohm high precision resistor (you may also use a Linear Potentiometer within the range of 0 to 50 ohm), follow the steps below to calculate the offset error.

1. Set the module to Full-bridge reading
2. Connect one of the 600 ohm resistor between Vexc and Vin+
3. Connect the 25 ohm resistor (R1) between Vin+ and Vin-
4. Connect the other 600 ohm resistor between Vin- COM as shown in the picture below.

For this example, the true value is 20.408 mV/V which is calculated by formula below:

True Value-= R1/(600+R1+600)

The offset error is calculated by comparing the true value with the reading in the FieldPoint Explorer. When you build your own resistor network, make sure that you do not exceed the current limit for the module, which is 21 mA. For more information on specifications, please refer the FP-SG-140 Operating Instructions Manual linked below.


Related Links: Product Manuals: FP-SG-140 Operating Instructions

Attachments:





Report Date: 01/29/2003
Last Updated: 02/14/2004
Document ID: 2TSBKQVS

Your Feedback!	Poor  |  Excellent							Yes	No
Document Quality?							Answered Your Question?
	1	2	3	4	5
Document needs work? Please tell us why.
Please Contact NI for all product and support inquiries.