Reading analog channels on USB-1608g

[juan.salcedo]

I am reading channels on a USB-1608g it appears to be ok when i have all of the channels plugged into sensors but when i unplug some of the sensors it looks like i start getting repeated data in the channels that were unplugged.

I am wondering what happens to the data map in the device when the sensors are disconnected? 

does the device shrink the array of data so that when i am reading data i am not reading data out of order and perhaps overflowing because i am trying to read more data than active channels? 

I'm trying to debug this remotely so i can't run the VB and watch the variable arrays coming back.

Juan

 

[Fausto]

Hello @juan.salcedo.

If you disconnect a sensor from an enabled channel, then the open channel will float and pick up signals from enabled adjacent channels.  If you intend to disconnect sensors from enabled channels, then you should short the channel.  Otherwise, disable any open channel.

There is no impact on the data array, unless you remove open channel(s) from the list.

Regards,

Fausto

[juan.salcedo]

Thank you @Fausto

Ok ... That makes sense about the adjacent channels floating and picking up signals. That was my second guess on what was going on with this unit.

What is the command for disabling a channel dynamically? Does disabling a channel remove the channel from the list and will I have to then handle the array to accommodate the removal (disable of the channel)?

Would using the module in differential mode eliminate the channel float?

Is there a way to tell if a sensor is disconnected and then program something to dynamically disable the channel or set an alarm? 

Besides the fact that I was getting readings that don't make any sense. I have to come up with a solution for the event where we have a sensor failure or broken wire during testing. How will I know when or if this happens and whether or not the data I am getting is still valid? 

 

Juan

 

Edited August 8, 2023 by juan.salcedo

[Fausto]

@juan.salcedo,

If performing an analog input scan, then you will need to stop the scan, remove the unwanted channels from channel/gain queue, and then restart the acquisition.  Alternatively, you would physically short the input terminals of analog input channels and leave the channel/gain queue or analog input channel range as is.

It is not good practice to leave analog input channels open during an acquisition, whether the channels be configured as single-ended or differential.  

On 8/7/2023 at 12:00 PM, juan.salcedo said:

Is there a way to tell if a sensor is disconnected and then program something to dynamically disable the channel or set an alarm? 

Before starting the analog input scan, call a single read on all desired channels and evaluate the measured results with expected results.

On 8/7/2023 at 12:00 PM, juan.salcedo said:

Besides the fact that I was getting readings that don't make any sense. I have to come up with a solution for the event where we have a sensor failure or broken wire during testing. How will I know when or if this happens and whether or not the data I am getting is still valid? 

You will need to compare the measured data with what the expected results would be.

Regards,

Fausto