F Ermazze

Hello all,

I am new to this forum. I hope to be in the good section

I need to produce an AC current at different frequencies with a Keithley 6221 current source.
Then, I need to measure the induced voltage drop across a resistance (RTD) at all the frequencies produced, by using an Ametek 7230 lock-in amplifiers, phase locked with the current source.

I managed already to lock the lock-in amplifier to the source by using a phase marker output from the trigger link cable (as explaned here https://forum.tek.com/viewtopic.php?t=45)

However, I have problems at low frequencies. The lock in is not quite well phase locked to the source. 
I believe this comes from the fact that the phase marker is not a TTL signal as requried by the lock-in amplifier (I also checked this with an oscilloscope).

Is there a way to output a TTL signal from the Keithley trigger link cable, so to properly lock the Lock in amplifier?
If so, how can I setup that?

Thank you very much
Best wishes
Federico


Ps:
Here is what I tried without success:
I tried to pilot the Keithley source by the lock-in (so the inverse). However, I only managed to trigger the source at the frequency of lock inm but I could not really lock the two. For example, the Keithley starts to send a wave at each trigger signal from the lock-in but the form and frequency of the wave that it generates is not dependent on the lock-in (for instance, I can send many portion of a 100 Hz sine wave at a 2kHz frequency set by the lock-in. I could manually set the two frequencies to be the same, but I think this may cause errors in the measures since the waves will never be properly synchronised) 

Thank you very much for any help you can give!