ADC 22 connections

I have an ADC 22 and two ADC 16 units. The measurements obtained via these units, in particular the ADC 22 seemed suspect.

To prove this I shorted all ADC 22 inputs to the two ground pins on the connector via a 25Way D "test" connector I made up. All readings were no where near zero. I found that if I connected mains earth to the ground inputs on the test connector then Channels 1 through 5 and 14 through 19 all showed zero whilst channels 6 through 13 and 20 through 22 all showed full scale.

On the ADC 16s, testing in a similar manner also showed that mains earth is needed on the ground inputs before the readings were correct.

Borth the ADC 16s are connected to the computer via a USB to RS232 port expander and the ADC 22 is connected via your USB to parallel adaptor.

What is going on?
I await your response.

Hi

Thank you for your post.

It is true that the inputs need to be grounded to read zero - otherwise they float. This does not affect the readings.

With the ADC-22 it is a little unusual that some are reading full scale. It may be that this needs repairing. If you ground just these channels, do they still do it?

Best Regards

Hello.
Half the channels are at full scale and the other half are at zero when all the inputs are shorted together and grounded.

Can I conclude that all your logger units are not referenced to mains earth via the Com and or LPT ports and PC power supply?

Hi

Thank you for your post.

The channels do find their ground via the computer. Sometimes, for instance on laptops with switch-mode power supplies, this is not possible.

I would suggest that if your channels are always showing the maximum voltage then the unit may be faulty. I have tried to replicate this here and am unable to do it - when I ground channels on the unit then they always go to zero.

If you believe the hardware is faulty and woud like it fixed then please email us with your full contact details and a link to this thread so that we can issue you with a returns number.

Hope this helps

Best Regards

Hello Sarah.

I now believe the ADC 22 does have a fault and therefore need to return it. We purchased it about 1 month ago. Please send me an email address where to send the contact details. Does it matter that we bought it throuigh your USA rep as we are based in San Diego California.

I await your response.

Hi

Thank you for your post.

You can still return it to us even if you bought it through a distributor. Please send you full contact details and a link to this post to tech@picotech.com and I will then be able to issue you with a returns number.

Best Regards