What accuracy of precison resistors do I need for shunt calibration

[AMP12]

I need to perform a shunt calibration on an SCC 2345 SG-24 strain gauge module with a load cell transducer.  Apparently shunt resistors are not included with the modules so I need to buy some.  My load cell has 350ohm bridge legs.  I was previously told that precision resistors need to be used for strain gauge applications. What accuracy is considered precision, 1%, 0.5%, 0.1%? What diameter lead wires are needed?

I was unable to find anything on the NI website.  Can anybody recommend a supplier?

[Henrik_Volkers]

You don't have to care about the tolerance, as long as you can measure your resistor 🙂

However, what you need is (long term) stability and a low temperature coefficient.

Size: in my SCXI-1321 terminal manual  it's named a 1/4W resistor ...

Supplier: Vishay makes good ones, but I don't now if the size will match.

[Logan_K]

Hello,

The easiest way to perform shunt calibration with your SCC-SG24 module is to use a SCC-SG11 module. This module has a shunt calibration resistor built into it, and can be easily controlled from software. Page 22 of the SCC-SG user's manual (http://www.ni.com/pdf/manuals/371073b.pdf) describes how to connect a SCC-SG24 module up to the SCC-SG11 to perform a shunt calibration.

Logan Kunitz

SCXI R&D

NI-Austin

[AMP12]

Sorry, I guess I was too quick with my message and didn't double check it.  I actually need to do an offset null adjustment (which the SG-24 doesn't include resistors) with a 30k ohm resistor and then do a shunt calibration at 60k ohms.  The SG-11 has a 301k ohm resistor.

So knowing that I need a long term stability and low temperature coeffienent, what % accuracy resistance I would need for the offset nulling?  I see from the manual that the shunt resistor is 1%.

[AMP12]

Additionally, I can measure resistance accurately, but the temp coeff. is my concern.

[e-Cash-Money]

Hello Clampy,

Two of the 30 kOhm resistors for offselt nulling should have shipped with the SCC-SG24.  If you need to buy new ones, here is the information on the resistor we ship with the SCC-SG24:
Xicon, 1/4W, 1%, Metal Film Resistors, 30Kohms, 1%, 50PPM - RoHS/Pb-FREE per producer documentation