Data Acquisition with Honeywell Load Cell 31

[rubberduckiness]

Hi all!! I am currently trying to acquire load data with a Honeywell 31 load cell connected to the NI 9237. The samples are then displayed as an average.

While the code has no errors, the averages are not correct - a higher load returns a negative value or one smaller than when there is no load. The VI is attached, and I would really appreciate some pointers.

Also, as this is my first time connecting the 9237 and the Honeywell load cell via a NI 9949 module, I just want to double-check that my connections are right:

Honeywell    ---->    NI Pin #

+ output                 2

-  output                 3

+ excitation            6

- excitation             7

Thanks a bunch!!!

[-lucho-]

Hello,

I verified the connection diagram with the connection you did and those seem right.

However, if this is a full bridge sensor keep in mind that the you must connect the AI+ and AI–, EX+ and EX–, and RS+ and RS– signals as  listed in the manual of the NI-9237

Regards, 

Luis A.

National Instruments

[rubberduckiness]

Thank you for your verification. However, the Honeywell Model 31 load cell has only 4 wire connections, and I use a RJ-50. In addition, could you please take a look at my VI for data acquisition and averaging? The data collected seems to be off.

Thank you so much for your time.

[Brad_K]

Hi rubberduckiness,

How "off" is the data? How does it differ from what you expected?

Are you using TEDS? Your VI seems to, but you said the load cell has only 4 wire connections.

There's a shipping example that demonstrates the load cell support that was added in DAQmx 9.1. I think that would be a better starting point, since it scales to force/weight units: https://decibel.ni.com/content/docs/DOC-12259

Brad

[rubberduckiness]

Hi, Brad. I thougt I was using TEDS (or at least that's what I ordered from Honeywell), with the load cell connected to the 10-pin NI 9949, which connects in turn to the 9237 via a RJ-50 wire. Was there a component I missed?

With respect to data, what I mean is that the average values with applied loads are not in a linear fashion. In fact, sometimes they are negative, even when I had the offset nulling on. The load cell output an expected response to increased load when I test it in the Measure and Automation Explorer, but somehow the VI makes the data screwy.

Thank you for your help.

 - Katherine

[KatieC]

Katherine, 

I took a look at the Honeywell 31 data sheet. If you look on page 3, there is a table called option codes. If you got option 53t, then it would be a TEDS device. Not all Honeywell 31s are TEDS. Since yours has 4 wires, you most likely didn't get a TEDS device. However, it looks like if you have one of these it will allow you to use your device with the NI 9237 as a TEDS. 

The reason your code may not be working correctly is because it is configured for a TEDS device, and your sensor isn't. Once you obtain the part mentioned above from Honeywell, it may start working. Let us know!

Katie

[rubberduckiness]

Hello, Katie. Thanks for the response. While my Model 31 transducer did not have a TEDS, I also purchased the NI Cable assembly with screw-terminal to RJ-50 with mounted inline TEDS on the cable. Should that have worked?

 - Katherine

[KatieC]

Katherine, 

I can't seem to find the cable you are describing. Do you have a part number for it?

Thanks!

Katie

[rubberduckiness]

Hello, Katie. My original order form is attached. I circled both the model 31 load cell I bought and the TEDS cable.

Thanks!

Best, Katherine

[KatieC]

Katherine, 

My apologies--I misunderstood; I thought it was an NI cable as in purchased from NI. I found the part on the Honeywell site, and when you click data sheet it is the same link I posted earlier. Honeywell advertises this as a way to allow you to use your device with the NI 9237 as a TEDS--so in short, yes, this should work fine!

Katie