1215CPU Problems converting 0-20mA output to 0-10VDC

I need to convert the Analog output on the 1215C CPU from 0-20mA to 0-10 VDC.

I have placed a 500Ω resistor across 2M and AQ1 terminals.

I then force 100% output through my code and when I measure the voltage across the terminals, I don't read any voltage.

Any ideas as to what I am missing?

Hi,

First of all for 4-20mA to 0-10V it is not possible with 500ohms resistance. As per ohms law

0.004A x 500ohms = 2V.

Have you configured channel of respective analog output with 4-20mA? 

I have revised my topic to convert 0-20mA to 0-10VDC.

The 1215c Analog outputs can only be configured as 0-20mA, no other options are available.

Thanks,

John

Hi John,

1215 CPU specs say: Output drive impedance ≤500 Ω max. What if you tried something slightly lower than 500 Ω just to test.

Regards,

Adam

Yes, 2M is connected to the common of the system (this is also tied to M and 1M at different parts of the PLC).

Thanks!

Good call.

I tried a 480Ω resistor across 2M and AQ1 terminals with no change.

Across 2M and AQ1 is 0VDC.

kind regards,

John

Here's the test points I've tried:

QW66=

16#25BC  = ~35% (expect to see ~ 3.5V)

16#4B78 = ~ 70% (expect to see ~ 7.0V)

16#6BD0 = ~ 100% (expect to see ~ 10.0V)

In all cases 0.0VDC output across 2M and AQ1.

Kind regards,

If you are always getting 0V, then

1. You are writing to the wrong output word

2. You still have a wiring problem

3. You broke it.