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Old 4th May 2012, 09:15 PM   #141
NicMac is offline NicMac  Italy
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Default and completely dumb question.......

How do I plug in the jfet pins (gate, source, drain) into the base, emitter and collector slots
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Old 5th May 2012, 01:54 AM   #142
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G = B
S = C
D = E

I think but is you use the component tester it can recognize the DUT and tell you a bit more

I am not near it at present but I can look later and report back
There are a couple of test for J fet in the menu
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Old 5th May 2012, 09:57 AM   #143
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Quote:
Originally Posted by locky_z View Post
'The big relays (J1 and J2 ) get very warm' is normal.

The relay coil resistor is about 1K, so under 24V supply,It will consume 0.5W.


You can change LM317 output voltage, reduce 24V to 20V,because relay can also work in 20V.
24V power supply is only available to the relay power, and followed after 7812, a 12V power supply to the DAC.
Therefore, 24V reduced to 20V, will not impact on 7812.
Hi Locky_Z

Does it mean I can change all the relays to 12V ones and just modify LM317 output to 12V ?

Reason for doing this is I prefer new components than second hand and I happen to already have Omron 12V ones in stock

Thanks!

Fred
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Old 5th May 2012, 03:11 PM   #144
locky_z is offline locky_z  China
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to Lazybutt:
Yes,you can change LM317 output to 12V, and change relays to 12V,
And you also need to remove the 7812. because 7812 is powered by LM317.


to NicMac:
measure FET ,you can insert G to B / S to E / D to C
and press 'Load Condition' button to load ‘N-JFET Vgs-Id(Fix Vce)’ measurement conditions,
Click the image to open in full size.
The measurement conditions mean
1. It set Vb from -5V to 0V step 0.1V mean Vgs from -5V to 0V step 0.1V
2. Set constant Vce=10V mean Vds is fixed at 10V.
3. RB=6K mean Gate protect resistor choice 6K ohm
4. RC=75 mean drain current sample resistor is 75 ohm.
5. Imax=30mA mean measurement end at current reaches 30mA.
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Old 7th May 2012, 09:10 AM   #145
NicMac is offline NicMac  Italy
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locky_z,

To hopefully improve further this already very nice device I will be upgrading some components.

Firstly, I will be changing the current setting resistors to precision resistors with low temperature coefficients. I think I will need to calibrate the instrument after changing these components. Can you please instruct us how to do the calibration?

I will also relocate Q1-Q4 and replace these with new components. Do you have any suggestions what components to get for Q1-Q4?

Thanks for the help!

Nic
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Old 7th May 2012, 02:41 PM   #146
locky_z is offline locky_z  China
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Quote:
Originally Posted by NicMac View Post
locky_z,
Firstly, I will be changing the current setting resistors to precision resistors with low temperature coefficients. I think I will need to calibrate the instrument after changing these components. Can you please instruct us how to do the calibration?
The temperature coefficients of current resistor is not very import.

Quote:
Originally Posted by NicMac View Post
I will also relocate Q1-Q4 and replace these with new components. Do you have any suggestions what components to get for Q1-Q4?
Nic
Q1~Q4 need Darlington,Hfe>1500 Vceo>50V Icmax>8A,Pdmax>65W
such as tip142 147
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Old 8th May 2012, 07:50 AM   #147
NicMac is offline NicMac  Italy
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locky_z,

Thank you for the answers, I have a few more:

I have noticed that checking the box "calibrate" before measurement does not increase much the measurement time.
Does it improve the quality of the measurement?
Is it best to always choose this option?

How many curve traces can a file hold reliably before making the software unstable?

If I replace RC 4.55R with a 4.7R value how do I calibrate the device afterwards?

Thanks,

Nic
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Old 8th May 2012, 09:02 AM   #148
locky_z is offline locky_z  China
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Quote:
Originally Posted by NicMac View Post
locky_z,
I have noticed that checking the box "calibrate" before measurement does not increase much the measurement time.
Does it improve the quality of the measurement?
Is it best to always choose this option?
The "Offset test" button is used to measurement "the error in different common mode voltage”, if you see the absolute value of Y-Axis more than 0.005V, mean need to check the "calibrate before measurement " and then re-press the "Offset test" button,
the system will calibrate again and use the new calibrate "parameter" on follow-up measure, so you only check the "calibrate before measurement " once is enought.
if you exit program or check "calibrate before measurement " have more then 30min,you may need to check it again.


Quote:
Originally Posted by NicMac View Post
How many curve traces can a file hold reliably before making the software unstable?
Nic
a file can hold more 500 curve,

Quote:
Originally Posted by NicMac View Post
If I replace RC 4.55R with a 4.7R value how do I calibrate the device afterwards?
Nic
yes ,you need do a "current calibrate“ again.
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Old 8th May 2012, 11:04 AM   #149
NicMac is offline NicMac  Italy
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Thank you very much!

Quote:
Originally Posted by locky_z View Post
yes ,you need do a "current calibrate“ again.
How is this procedure performed? How do I enter the new value for RC in the software?

Cheers,

Nic
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Old 8th May 2012, 11:14 AM   #150
E007 is offline E007  China
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Hi, locky_z,

So glad to see your design here and share with overseas friends.
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