Tektronix Technical Forums are maintained by community involvement. Feel free to post questions or respond to questions by other members. Should you require a time-sensitive answer, please contact your local Tektronix support center here.

Keithley 236 Triaxial to Coaxial conversion

200, 210, 220, 486/7, 60x, 61x, 64x Electrometers
409, 41x, 42x, 44x, 48x -
14x, 18x, 1801 Nanovoltmeters
15x, 18x Null Detectors/Microvoltmeters
Post Reply
lasergeek
Posts: 1
Joined: May 29th, 2013, 5:47 am
Country: United States

Keithley 236 Triaxial to Coaxial conversion

Post by lasergeek » May 29th, 2013, 6:04 am

We are using labview software to control our Keithley 236 SMU and mainly perform IV curves on photodiodes. We are attempting to use the standard configuration on page 4-12 of the 6th Edition of the Keithley Low Level Measurements handbook. However, we attached triax to coax converters to SMU High and Lo and performed a voltage source/current measurement and found it to be open. This is good since we had nothing attached to the SMUs. Then we attempted a measurement by attaching two coaxial cables to SMU High and Lo and saw a resistor like behavior which was shifted from 0.0 volts. I should point out that these coaxial cables were not attached to anything, just an open circuit. Can someone explain to me why an open circuit looks like a shifted resistor curve? (looking at logarithmic current scale) Thanks in advance!!

Dale C
Keithley Applications
Keithley Applications
Posts: 2845
Joined: June 10th, 2010, 6:22 am
Country: United States
Contact:

Re: Keithley 236 Triaxial to Coaxial conversion

Post by Dale C » May 29th, 2013, 12:11 pm

I can understand the triax to BNC adapter on the SMU OUTPUT HI.
But not on OUTPUT LO.
Becasue OUTPUT LO is a banana jack and/or the inner shield of SENSE LO.
So maybe the connections are incorrect?
Try this.
Use the triax to coax adapter on the OUTPUT HI. Connect the center pin to one side of the resistor.
Take a banana plug to clip lead cable into the OUTPUT LO banana jack . Connec the clip lead to the other side of the resistor.
If you have a 1k ohm resistor, Output 1mA and see if you measure 1V.

kunnysensei
Posts: 5
Joined: December 10th, 2012, 2:15 am
Country: Australia

Re: Keithley 236 Triaxial to Coaxial conversion

Post by kunnysensei » April 10th, 2014, 8:28 pm

you have to be careful which Triax to BNC adapters you use, because they come in different versions, i.e. leaving the middle shield floating or connected to the outside shield. please have another look at this.

Dale C
Keithley Applications
Keithley Applications
Posts: 2845
Joined: June 10th, 2010, 6:22 am
Country: United States
Contact:

Re: Keithley 236 Triaxial to Coaxial conversion

Post by Dale C » April 11th, 2014, 6:22 am

Yes, I agree with your statement.
I would recommend the Model 7078-TRX-BNC.
This is a triax to BNC adapter that leaves the outer shield of he triax behind.
It does not connecto the inner shield to the outer shield.
I have seen this many times and it limits the high voltage on a 237 to about 150V>
So use the 7078-TRX-BNC from Keithley.

Post Reply

Return to “Older & Obsolete Instruments”

Who is online

Users browsing this forum: No registered users and 1 guest