calibrate usb-6009 ?

[pabbott]

Is it possible to calibrate the usb-6009? 

I have the leads connected together and measure -0.7 volts (should be 0).

I'm using VI logger and NI SignalExpress.

Thanks

[Dennis_Knutson]

What leads connected to what exactly? If you want to measure 0 volts, the ai inputs should be connected to gnd.

[pabbott]

Hi Dennis, 

The analog channel is set up in differential mode, and AI0+ and AI0- are connected together.

[Dennis_Knutson]

Try setting it to RSE and grounding the inputs.

[Henrik_Volkers]

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pabbott wrote:

Is it possible to calibrate the usb-6009? 

I have the leads connected together and measure -0.7 volts (should be 0).

I'm using VI logger and NI SignalExpress.

Thanks

---

Probably due to BIAS currents of the inputs, with some additional OFFSET . 

Providing a BIAS resistor (path) to GND help with the currents, for the offset voltage this lowcost device offers no tuneable compensation (but can be compensated by software, but might drift with time and temperature, see specification). 

Search the KnowledgeBase or the user manual for BIAS resistor location and value and connecting diagrams.

Message Edited by Henrik Volkers on 02-09-2010 03:53 PM

[Mr.F]

I’m curious as to the outcome of grounding the inputs. Its sound like your board may be reading incorrectly. How old is this device? If you decide you need to send the board in for repair you can take a look at this procedure.

[pabbott]

Thanks for the suggestions.

The device is several years old and has been used quite a bit.

Grounding all channels and setting to RSE mode reveals that one channel has a large offset (~1v).  Most channels show less than 0.1v offset, but one channel is apparently damaged.

I don't suppose it's worth the money to have it repaired.  We can use the other channels for now.  I was dissapointed that there is no user calibration possible in the software.  I'm also dissapointed about the apparent low quality of this device.  I understand that it is a "low-cost" device, but I guess I expected a more robust device since it carries the NI name.

We mainly test batteries and battery protection circuits (PCM) and chargers.  We test charge currents and voltage cutoffs and we plot charge profiles.  Most of the time accuracy is not critical and the voltages are below 10V (barely).  Current measurements are done with 0.02 ~ 0.10 ohm sense resistor.  

Can someone suggest a better device (similar to the USB-6009) that would fit our purposes and is not too expensive?

Thanks.

[Mr.F]

Sorry you’re disappointed with that product; after years of use component will vary and drift in value. Unfortunately this device does not support calibration.

If you’re unsure what a better device might be for your application you can call (888) 280-7645 and speak to a technical sales representative and they will be able to discuss with your what you need in a DAQ device.