can counter output be fed into a simple voltage divider?

[invasion2121]

I have successfully installed this labview program: http://www.ni.com/white-paper/2991/en

and I know it works because I can see a pulse train in the oscilloscope when connecting to the counter terminal on the BNC-2110 block. 

I am using a DAQ pci-e 6259 board. 

I noticed the amplitude of the signal is approximately 5V but I need it to be approx. 3V.  So I fed the pulse train into a simple voltage divider circuit that looks like:

V1 above is actually the PWM signal coming out of the counter terminal from the BNC-2110 block.  However, when I measure the amplitude on the oscilloscope it is still like 5V (or maybe like 4.9).

Am I missing something big here?

[Chris-NI · Accepted solution]

Hi invasion2121,

There should be no issue with dividing the voltage output of your counter.  Your picture was cut off slightly at the top - are you probing voltage drops across R7 where you're seeing 4.9-5 V?  What does the voltage on the rest of the circuit look like?  The counter output won't deliver more than 5 V from output to ground, so if R7 is dropping most of that, then your voltage on R1 and R2 would have to be nearly 0.

What is the impedance of your scope?  This may have an effect on your measurement, but not like you are describing.

Regards,

[invasion2121]

You're right.  I did not ground the circuit correctly.