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6221 with lock-in amplifier

6220, 6221 Current Sources
jvincent
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6221 with lock-in amplifier

Post by jvincent » June 10th, 2010, 11:30 am

Is it possible to sync 6221 with lock-in amplifier (SR830)?
I'd like to use the 6221 for providing sine output currents and reference the frequency to the lock-in amp. If there's a cable connecting the Trigger link from 6221 to Ref_in of SR830, please send use the quote. Any other suggestions would be appreciated.

Dale C
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Re: 6221 with lock-in amplifier

Post by Dale C » October 25th, 2010, 11:10 am

Use the Phase Marker output pulse to track for the Lock in amplifier.

existenz1982
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Re: 6221 with lock-in amplifier

Post by existenz1982 » January 13th, 2011, 9:50 am

I'm trying to connect 6221 to lock in amplifier sr530 as reference signal, I understand that I have to connect the trigger link to sr530 (BNC connector) but I don't understand how should I do it.
Can you please help me with that problem.
Thanks.

Tom Sw
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Re: 6221 with lock-in amplifier

Post by Tom Sw » January 13th, 2011, 10:00 am

You can create your own adapter or you can purchase the Keithley 8502 Trigger Link adapter that converts the Trigger Link cable to BNC lines.

fchen0000
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Re: 6221 with lock-in amplifier

Post by fchen0000 » March 13th, 2011, 2:42 pm

I also wanted to feed the current to my SR830 lock-in.
Instead of buying the expensive Keithley 8502 adapter, I cut an old serial mouse and broke the center plastic so it goes into the trigger link cable. According to the manual, the phase mark is defaulted to trigger link #3, so just connect the ground pin 8 to a BNC male's ground and connect the pin 3 to BNC's pin.

So far so good but oops, SR830/850 does not accept pulse as external reference. (Some other lock-ins, e.g., SR844, can use pulse as external reference ...)
Guess one needs a circuit to convert the pulse to a square or sine wave (w/o phase shift) ... Any clue?

Dale C
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Re: 6221 with lock-in amplifier

Post by Dale C » March 14th, 2011, 10:01 am


scal_pas
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Re: 6221 with lock-in amplifier

Post by scal_pas » April 6th, 2011, 8:44 am

Hi

I also use a 6221 with a SR830 lock-in, with a home made adapter like you. On the 830's REF IN, I set Trig to POS EDGE and it works fine. Have you tried this ?

KKirsh
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Re: 6221 with lock-in amplifier

Post by KKirsh » May 26th, 2011, 2:14 pm

I made the trigger link adapter cable and can now connect to the SR 830 ref in input and I tried changing it to POS EDGE, but still nothing. What do the TRIG setting on the 6221 need to be to output to the SR 830? Has anyone gotten this to work yet?

scal_pas
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Re: 6221 with lock-in amplifier

Post by scal_pas » June 15th, 2011, 8:35 am

Have you done this ?
by Dale C » October 25th, 2010, 1:10 pm
Use the Phase Marker output pulse to track for the Lock in amplifier.
because by default the phase marker is deactivated. Then use pins 3 and 8 (from memory) to connect to the lock-in input, and it should work.

Dale C
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Re: 6221 with lock-in amplifier

Post by Dale C » June 15th, 2011, 1:58 pm

I have not used it with a lock-in amplifier.
But the phase marker is easy to enable.
Press CONFIG, let go,
Press WAVE, let go.
Select PH-MKR, press ENTER.
Select STATE, press ENTER.
Select On, press ENTER.
Select OUTPUT-POINT, press ENTER.
Select the degrees of phase you want the pulse to appear.
Press ENTER.
Select OUTPUT LINE, press ENTER.
Select the output line.
That should do it for the Phase marker,

berger.156
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Re: 6221 with lock-in amplifier

Post by berger.156 » September 7th, 2011, 3:13 pm

I have a Model 8503 DIN-to-BNC Trigger Cable which I was hoping to use to provide the reference input on an SR850 lock-in. I've followed the steps outlined below (posted originally by Dale C, to which I've added a few things):

Press CONFIG, let go,
Press WAVE, let go.
Select PH-MKR, press ENTER.
Select STATE, press ENTER.
Select On, press ENTER.
Select OUTPUT-POINT, press ENTER.
Select the degrees of phase you want the pulse to appear (I set this to 180deg. Not sure what it should be).
Press ENTER.
Select OUTPUT LINE, press ENTER.
Select the output line (I set this to #1, as that should be the center conductor on one of the BNC outputs of the 8503 cable)

I then press WAVE, TRIG. However, I see nothing on the trigger line as observed on an oscilloscope (expected some trigger voltage pulse (TTL or sine wave) at the frequency of the WAVE). Have I done something incorrectly?

scal_pas
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Re: 6221 with lock-in amplifier

Post by scal_pas » December 2nd, 2011, 2:10 pm

That should work. If you choose #1 as the output line, then you should then measure the trigger signal between #1 and #8 (ground).The pulse is very short though, about 1 µs, so you may have to zoom in a bit to see it.

kemege
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Re: 6221 with lock-in amplifier

Post by kemege » February 14th, 2014, 10:54 pm

scal_pas wrote:Hi

I also use a 6221 with a SR830 lock-in, with a home made adapter like you. On the 830's REF IN, I set Trig to POS EDGE and it works fine. Have you tried this ?
I'm also trying to use 6221 with SR830, and I used a PS/2 port from an old keyboard to transfer trigger signals
As is said in the 6221 manual, the phase marker trigger signal should be a 1us, 5V pulse
But when I connected the line to a oscilloscope, I only saw 1us, 0.5V pulse signals, which is too low to be used as SR830 reference signals
Is there anything I did wrong so that I cannot get the correct signal?

Andrea C
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Re: 6221 with lock-in amplifier

Post by Andrea C » February 20th, 2014, 3:27 am

Hi kemege,

What is the input R of your scope? If it is low like 50 ohms, it may be loading the Phase Mark signal.
Make sure you have high input impedance setting on your scope/probe.

Andrea

tomigaya
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Re: 6221 with lock-in amplifier

Post by tomigaya » March 26th, 2014, 12:30 am

Dear all,
I have the same problem : I want to lock the frequency of the 6221 to the lock-in SR830.

Spending days and nights reading all the forum posts + looking an answer from google, scientific papers … still I cannot get any practical answer to this problem.

Hardware:
Keithley 6221 + keithley trigger cable model 8503 + SR830 + NF LI5640 lock in amplifiers.

The config on the 6221 was set up as indicated in this forum.
by berger.156 » September 7th, 2011, 6:13 pm
by Dale C » June 15th, 2011, 4:58 pm

I tried all the phase marker (#1 to #6). Phase is set to 0 or 180.
SR830 is configured accordingly
- Ref source : external
- External reference trigger : TTL rising edge

6221: WAVE, then TRIG -> the output ON/OFF is blinking.
I measure 4.91V at the output of the 8503 cable set with the phase marker #3. This BNC is connected to the ref in of the SR830. However the lock in indicates "unlock" even the configuration.
So now I am wondering why it does not work, and probably the 5V is too high.

I tried the same 6221 trigger connection to another lock in NF LI5640. It cannot lock.

But I succeeded in locking the LI5640 on the SR830. Now, when I measure the output signal on the trigger cable of the LI5640 (NF osc out --> SR ref in) I found it is ~5.7mV. That means 1000 times lower than the voltage at the output of the 6221 trigger cable.

I conclude that because of the high output voltage ~5V from the 6221 on the trigger 8503 keithley cable connected to the REF IN of any lock in amplifiers, both SR830 or the NF LI5640 are UNable to phase lock.

Next I will try to divide the voltage by 1000, and try again.

tomigaya
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Re: 6221 with lock-in amplifier

Post by tomigaya » March 26th, 2014, 2:57 am

… next then.
I made a voltage divider with 2 resistances 100 Ohm and 100k Ohm so that the ratio is 1/1000.
Then I checked the output voltage before and after the voltage divider. I got 4.9V and 4.7mV respectively.
Cable 8503 + voltage divider + BNC --> ref in of SR830
SR830 is still "unlock".

So finally, I took an agilent 33250A, connect the synchro output to the ref in of SR830. The ref in was "locked", it works.
The synch output of Ag33250A indicates 1.864V.

So I change the voltage divider with R1=56k ohm and R2 = 100k ohm. R2/(R1+R2)*5V = 1.8V. I got an output of 1.650V.
SR830 is still "unlock" state.

That means even the Ref in voltage is 5V or 1.65V or 5mV, the SR830 cannot be locked on Keithley 6221 even with the cable 8503.
Mysterious …

tomigaya
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Re: 6221 with lock-in amplifier

Post by tomigaya » March 26th, 2014, 4:51 am

Now I monitored the synch output of the agilent 33250A with the oscilloscope. I found square signal.
However, even setting 6221 parameters as described in previous posts, the output signal is a constant voltage, not square pulses.
This is the origin of the problem. I should have made the comparison before (means sorry for all previous posts …).

The question is :
Since standard configuration does not generate pulses , how should I change the 6221 parameters to get an trigger output signal that will be square pulses at frequency f ?

tomigaya
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Re: 6221 with lock-in amplifier

Post by tomigaya » March 26th, 2014, 11:23 pm

Dear all,
finally I succeed to lock the 6221 to a lock-in amplifier SR830 or NF LI5640. I will explain.

6221 - Trigger link ---> cable 8503 ---> REF IN of your lock-in (setting external reference source).

The cable 8503 has 8 pins connector plugged to the rear panel of 6221 Trigger link, and 2 BNC output based on RG58 coaxial cables.
From the 8 pins, only 2 pins are needed.
Pin number / Description
1 -- Trigger link 1
2 -- Trigger link 2
3 -- Trigger link 3
4 -- Trigger link 4
5 -- Trigger link 5
6 -- Trigger link 6
7 -- Ground
8 -- Ground

The position of the pins from the rear panel view ("x" means nothing) :
|_|
8 7 6
5 x 4 3
2 1

Here is the configuration I used on 6221
Select
Press CONFIG + WAVE

Phase Marker : ON
Output point :180
output line : #1 (important)
duration : infinite
ranging: best fixed
more
trig-mode: Man/bus
retrig: restart immediately
inactive value: 0

Press CONFIG + TRIG
arm-layer : arm-out
trig-layer : trigger-in

Here, rather than using the BNC output of cable 8503 with the mark "ext trig", I used the other one called "VMC". And it works !

How to know :
- take a multimeter, resistance mode, and check on which pin of your cable corresponds the BNC output of your cable 8503.
- take 2 wires, insert it into the rear panel of the trigger link of 6221, press WAVE + trig and then check with your oscillo which pin gives the pulsed signal (don't forget to select a SINE wave output of your ARB WAVE)


In short :
1- CONFIG + SETUP
select PRESET
2- CONFIG WAVE
select PH-MKR
STATE : ON
OUTPUT POINT : 180 or else
OUTPUT LINE (default is #3) : select #1 --> important
exit
3- press WAVE + TRIG
it works !

Sorry for all this long posts …

dmccann
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Re: 6221 with lock-in amplifier

Post by dmccann » May 20th, 2015, 4:41 am

Hi,

I'm attempting the same thing and found tomigaya's post helped to get it working.

Although I'm wondering which is more appropriate to use on the lock in 'Pos Edge' or 'Neg Edge' to lock on to the phase marker from the 6221? Looking in the 5221 manual (section 7-6) it seems to say the phase marker signal is a 1us pulse of 5V, but the way it is depicted in the manual shows a the pulse seems to actually be a drop from a high 5V to a low 0V so would not the Neg Edge (the first falling section) be the one which is aligned to the phase (ie 0deg, zero crossing) you specified? If I chose pos edge wouldn't that be the rising edge and hence 1us after the point I specified on the waveform?

Appreciate any help anyone can provide on this.

Dale C
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Re: 6221 with lock-in amplifier

Post by Dale C » May 20th, 2015, 6:07 am

That is correct.
The phase maker pulse is normally +5V.
When it outputs a pulse, it goes to 0V for the 1usec then back up to 5V.

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