Custom LabJack Analog Input Range in MWorks

Support
1

Hi Chris,

Hope you’re doing well. We’re working on a breathing experiment where we are trying to record thoracic and abdominal respiratory belt signals through a LabJack and log them in MWorks.

The belt interface outputs a very small analog signal, so when using the LabJack directly, we can configure a narrower analog input voltage range / higher gain to make the measurement more sensitive and get better resolution.

The issue we’re running into is that when we use the LabJack through MWorks, it seems like MWorks resets or overrides the LabJack configuration and uses the factory/default analog input settings instead. Because of that, we lose the benefit of using the smaller input range.

Is there a way in MWorks to configure a LabJack analog input with a custom voltage range or gain setting, rather than using the default range? Ideally, we’d like to set the input range to match these small respiratory signals so we can read and log them with better sensitivity and dynamic range.

Could you let us know if this is currently possible, and if so, how we should set it up?

Thanks!

Best,
Kanishka

5

Hi Kanishka,

Is there a way in MWorks to configure a LabJack analog input with a custom voltage range or gain setting, rather than using the default range?

This is not possible at present, but we could add support for it. I would probably add range_min and range_max parameters to labjack_ljm_analog_input. MWorks would then choose the smallest device-supported input range that encompasses the requested limits. Does that sound like it would work for you?

Cheers,
Chris

6

Hi Chris,

That would be perfect. One thing we would need, though, is the ability to set the range independently for each analog input channel.
For example, some channels in our setup would still need the standard -10 to +10 V range, while the respiratory belt channels would need a much smaller range, around ±0.01 V.
So as long as range_min and range_max are parameters that can be specified separately for each labjack_ljm_analog_inputchannel, that would work really well for us.
Thanks!
Best,
Kanishka

7

Hi Chris,

Just wanted to follow up on this when you have a chance. Being able to set range_min and range_max independently for each labjack_ljm_analog_inputchannel channel would work perfectly for our setup.

Please let me know if you think this would be feasible to add, or if there’s anything else you need from us.

Thanks again!

Best,
Kanishka

8

Hi Kanishka,

Sorry for not responding sooner. Yes, this should be no problem. I’ll try to get it done in the next couple of weeks.

Thanks,
Chris