Scaling Log Functions

Hi All,

We have a vacuum furnace controlled with a GE 90-30 PLC. The vacuum sensor outputs a 0-10mV signal to the PLC. The PLC is outfitted with a Horner mV input module (Set for +/-25mV) and automatically scales the 0-10mV signal over +/- 32000 units (we only use 0-12800 for the 0-10mV signal). We are trying to display the vacuum reading on a PC using Cimplicity HMI. My problem arises in trying to convert the values stored in the PLC to the correct units for vacuum. The 0-10mV form the sensor corresponds to 1x10-7 torr to 1x10-2 torr. So, how do I convert the values stored in the PLC (raw data) over the log scale of the vacuum readings?

Thanks in advance for any help.

Richard

Quite a few PLCs have log, log e and exponent functions.
If your PLC has these, you should have no problem.
Otherwise, you will have to look up the correct 'Taylor series' to convert the value.

Hope this helps,

Doug

Great,

I was hoping to stay away from Calculus for this.

Thanks for the insight.

Richard