PDM and resistive analog inputs?

Discuss issues and ideas you have to configuring displays with PowerVision
toni27
Posts: 11
Joined: Thu Nov 28, 2013 6:24 am

PDM and resistive analog inputs?

Post by toni27 » Tue Jun 23, 2015 4:55 am

Hi!

In several PDM specs and in the latest PDM reference manual (page 13) there are mentioned two resistive inputs (analog 1 and 2). The other six analog inputs (analog 3 - 8) are described as 0-5V inputs.

If I take a look at the PDM example downloaded from "Standard and Example Configurations" it seems that all analog inputs are measuring only voltage.

I couldn't find any settings for this in the IX3212-Manager of Powervision 2.7.
I suppose the pull-up and pull-downs described as settable at the analog input in the reference manual have to do with it.

Are the resistive inputs working and how can I set them up?

Best regards,
Toni
andymartyn
Posts: 25
Joined: Wed Oct 29, 2014 4:51 am

Re: PDM and resistive analog inputs?

Post by andymartyn » Tue Jun 23, 2015 6:51 am

This is what I have just been looking at and working with. Actually as we speak strangely enough, to read a fuel sender

The first two analog inputs are both resistive. They have a 2.2k pull-up resistor which isn't configurable unfortunately and you cannot use the nice features like pre-defined curves when using the IX32 inputs

When you map a variable onto these inputs you will get the voltage value 0 - 5V which you then need to work with. If you need the resistance then you need to convert back yourself. I used scripting as it made it easier for the interpolation but I am sure calculation events can be used based upon your needs

Code: Select all

double resistance = (pullupResistor * voltage) / (5.0 - voltage);
I defined the pullupResistor value elsewhere as a constant variable of 2200 (it is possible to create your own resistive circuit using the 5V outputs from the IX32s so I made it configurable) (Hopefully my calculations are correct :shock: )

I was able to read resistance to a minimum of 2.2 ohms per increment of voltage (5/1024) which for my needs was fine (I used a spreadsheet with the above calculation across the voltage steps to determine if it was accurate enough for my needs across the range of resistances I wanted to measure). When we used a 390 resistor I was able to read down to 0.38 ohms per increment

I would imagine using a PV780 display should be the same sort of range as the 390 I tested