Control.com - Nerds in Control

Dear All

we are using one controller for controlling DC drive and control analog out put is 0 - 11 volt but drive analog input is 0 - 9 volts. here I need to scale down the voltage in to 0 - 9 for running the motor in safe side

If you feed the voltage through 3 diodes in series, you would get approx. 2 volts drop. If the signal is bi-polar, you might need 6 diodes, 3 in each direction.

Bill Sturm

How about a voltage divider? If the input resistance is fixed, a series resistor may be your best bet. The only problem here is that the input resistance may not be stated or spec'ed. The analog output is probably fairly low impedance, but both are in the range where they may need to be considered in the equation for a precision divider. Since the ratio is small, I would try a pot in series and adjust for 9 volt in with 11 volts out.

Regards,
cww

The normal method of doing this is to use a signal conditioner module with a DC input and a DC output. You want one with adjustable (not fixed) scaling or calibration. You would then just calibrate it so that 0 to 11 volts input gives you 0 to 9 volts output.

There are lots of these available on the market. Talk to your normal suppliers of terminal blocks and instrumentation to see what they have on their shelves or can get easily.