cFP-AI-110 Incorrect Values for Switches

[rocksolidsr]

I have trouble getting switches to work with my cFP-AI-110, I have a linear transducer, a pressure transducer, and the output of a cFP-AO-210, going into the AI-110 and those are reading correct values, but I tried to put two swiches as inputs to the AI-110 also and when the swiches are open there is always some voltage on that input, but when I close the switch it reads the correct value, then when I open the switch again the input slowly decreases instead of going right to 0

I have included a picture of how I have everything wired if someone could please take a look and tell me if I have something wrong I would appreciate it.

[RavensFan]

Why do you have the analog output going to the V and C terminals of your analog input module?  You want V and C to be connected to your power supply.  Your wiring diagram makes it look like you are trying to use and analog output module to be a power source for your input module.

[rocksolidsr]

I wired it that way because I needed to measure the voltage that was supplying the linear transducer and pressure transducer to get accurate conversions and the AI-110 only measures voltages up to 10V.

So basically the analog output at 10V is the power supply for the LT and PT by using the Vsup terminals on the AI-110

is this not an acceptable way to do this?

thanks

[RavensFan]

---

rocksolidsr wrote:
I wired it that way because I needed to measure the voltage that was supplying the linear transducer and pressure transducer to get accurate conversions and the AI-110 only measures voltages up to 10V.

So basically the analog output at 10V is the power supply for the LT and PT by using the Vsup terminals on the AI-110

is this not an acceptable way to do this?

thanks

---

I would say no.  You don't want an analog output to be a power supply.  It probably wouldn't have the current capacity you would need to be a power source for other devices.  Have the 24VDC supply power your analog output card and your analog input card.  Then there should be enough juice to coming out of the Vsup to power the LT and PT.  If you need to measure the voltage of your power supply (and I'm not sure why you need to do this.)  You could used some high value resistors and create a voltage divider to get the voltage drop across the final resistor to be within the 10VDC range of an analog input channel.  About a 3:1 division should work fine.

How much current are your LT and PT expected to draw?  According to the manual for the AO-210 it can only source up to 10 mA per analog output channel.  So each device can only be getting 5 mA (or even less depending on how much is flowing through each switch.)