Turn on suggestions
Auto-suggest helps you quickly narrow down your search results by suggesting possible matches as you type.
Showing results for
Topic Options
- Subscribe to RSS Feed
- Mark Topic as New
- Mark Topic as Read
- Float this Topic for Current User
- Bookmark
- Subscribe
- Mute
- Printer Friendly Page
Maximum channel-to-channel voltage to multiple analog input lines.
gln103
Member
03-07-2005 02:02 PM
Options
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report to a Moderator
Thinking of using the SCXI-1102B 32 Channel AI board to measure individual voltage of 24 batteries wired in series. Each battery is ~1.6V max. Would be using Differential.
Is the ~40V that will be present between channels going to harm the board even though each individual channel will only see ~1.6v? I know there's this "Maximum Working Voltage" of +/-10V, but I guess I'm confused.
Thanks...
Is the ~40V that will be present between channels going to harm the board even though each individual channel will only see ~1.6v? I know there's this "Maximum Working Voltage" of +/-10V, but I guess I'm confused.
Thanks...
Buechsenschuetz
Active Participant
03-08-2005 02:42 AM
Options
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report to a Moderator
If your battery system is NOT ground referenced the ADC will see only the voltage of a single battery when measuring the differential voltage. However, in case there is any possible path to the reference ground of the ADC system from the battery system there is risk of leakage current through the multiplexer which might result in excessive voltage on the ADC inputs. There are no analog (semiconductor) switches without leakage current.
I once was involved in the design of a multi-purpose battery monitoring system. Since sometimes battery systems in UPS systems are ground referenced we had to use relays to switch over the differential inputs since leakage currents could not be avoided otherwise. We wanted to monitor up to 192 batteries (some UPS battery strings are that large) plus the total voltage and some other values and finally ended up in a system with more than 400 relays. But we finally managed to tame this beast.
I once was involved in the design of a multi-purpose battery monitoring system. Since sometimes battery systems in UPS systems are ground referenced we had to use relays to switch over the differential inputs since leakage currents could not be avoided otherwise. We wanted to monitor up to 192 batteries (some UPS battery strings are that large) plus the total voltage and some other values and finally ended up in a system with more than 400 relays. But we finally managed to tame this beast.
Otis
NI Employee (retired)
03-08-2005 04:12 PM
Options
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report to a Moderator
As Buechsenschuetz said, you shouldn't have any problem as long as you are measuring each one differentially and you do not have any of the batteries referenced to ground.
Even if you did happen to have them referenced to ground you should be okay, because the SCXI-1102B can handle up to +/- 42 V. That figure comes from the Product Data Sheet. You still can only read voltages up to +/- 10 V, but you could have up to 26 different 1.6 V batteries in series before you damage the device.
Even if you did happen to have them referenced to ground you should be okay, because the SCXI-1102B can handle up to +/- 42 V. That figure comes from the Product Data Sheet. You still can only read voltages up to +/- 10 V, but you could have up to 26 different 1.6 V batteries in series before you damage the device.
