I did a labview program that applies DC voltage across G and E terminals of IGBT (15V) using agilent 4155C and applies dc current across C and E teminals (50 mA) and measures the voltage across C and E terminals. The value should be around 0.7 V but the program is not giving me this value. It gives an oscillating value and after around 5 seconds it gives the correct value. How can I have the correct value directly because time is sensiive in my experiment. Can i get the correct value in the first half second?
I have a few questions that will help me assist you better. First, can you tell me how much your signal is oscillating? Second, how are you communicating with the Agilent 4155C (GPIB, etc.)? Finally, I looked at the Agilent 4155C/4156C User’s Guide Vol.2, Edition 5, and found that if you disable the SMU filter on your device, this might decrease the settling time. Thanks!
Thank you or your help. I am using GPIB-USB interface. First the value is increasing from 0.2V till 3.9 V and then decreasing to 0.7 V ( it takes 60 sec to to give around 0.7 V at room temperature the first time i try it and then if I try it again right after the first time it takes less time because it oscillates to 2 V and then decreases to give 0.7 V). I want to use this agilent in an experiment where other equipments are running too and my aim is to have the correct value within the first 0.2 sec. Can I do this? I attached a test program which I used.
Thanks for your test program. Can you describe in detail the experiment you are trying to perform? The big picture will help me see this issue better. Also, who is the manufacturer of your IGBT? Finally, exactly what signal are you sending to your IGBT and how will it change over time? Thanks!
First, in the test program I am just turning the 4155c on, applying 15 V DC voltage across G and E terminals and 50 mA DC current across C and E terminals. name of IGBT:G4BC30KD. From literature, it should give around 0.7 volt across C and E terminals. As for, in the original program, I am performing thermal cycling on IGBT.
aging the IGBT, I am giving a square waveform signal across Vge using function generator and DC voltage across C and E terminals using a power supply(I), and there is another power supply to turn on the current sensor found in the circuit which is always on. The function generator and the power supply(I) is controlled by labview and they are on during the heating of IGBT. During cooling of IGBT, they are off and then the 4155C is on.thus, time is sensitive because I want to have the measurement from the 4155C rigght after the function generator is off ( at a high temperature). However as a test program, I am just turning the 4155C on and the power supply that turn on the current sensor. From literature, I know that the value of the Vce should be only affected by temperature if you are giving constabt voltage across Vge. So, in the test program, it should give me directly 0.7 V.I am wondering if there is something wrong in the labview program. Should I add another blocks that can control the time?
Thank you for your help
I think this description also makes the issue clearer:
I am able to output DC voltage (15V) across G and E terminals of an IGBT and to output 50 mA DC current across C and E terminals and measure the voltage across C and E terminals. It should give me a value around 0.7 V. I am facing 2 problems. The first that the 4155C is not giving 15 V, it is just givng 8.5 V as a status that it is reaching its compliance though I am giving a cmpliance of 0.1 A ( In the manual the compliance corresponding to 2V<Voltage<20V is 0.1 A). Moreover, when i am placing the iGBT in the board that sockets also a current sensor ( the current sensor is turned on by power supply of 15 V), the 4155C gives 5 V and then increases to 8 V. Thus, the measured value of Vce is oscillitating to reach 3 V and then gives 0.7 V. In my experiment, I should have the correct value directly.
Can you tell me what literature you are referring to when you said "From literature, it should give around 0.7 volt across C and E terminals." please? I'd like to look into this issue a little more before I give you a definite answer.
Also, regarding the 4155C not giving you the correct voltage, I'm afraid I won't be able to help much with this issue. It appears to be a problem with your hardware so I would suggest contacting the manufacturer to try to find a solution.
The code you have posted looks correct so I'm trying to isolate where the problem is exactly. Thanks!
Thank you for you help. Can I isolate the problem from the labview program? I want to be sure that it is not from the labview program. Do you suggest another way of doing the labview program.
Thank you again
Unfortunately I do not think you will be able to isolate this issue with your LabVIEW program. The only suggestion I have would be to add a delay before you read the data. However, due to your time sensitive issue, I don't think this would help you. Due to the physics of your hardware, I don't think the .2 second settling time is possible.