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Old 8th May 2012, 12:37 PM   #151
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Quote:
Originally Posted by E007 View Post
Hi, locky_z,

So glad to see your design here and share with overseas friends.
Shared, and very much appreciated here ! This is a great design!
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Old 8th May 2012, 02:30 PM   #152
locky_z is offline locky_z  China
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Quote:
Originally Posted by NicMac View Post
Thank you very much!
How is this procedure performed? How do I enter the new value for RC in the software?
Nic
goto "options"->Config->Relay and Resistor Define
The field value(OHM) is the current sample resistor value define.
The b7~b0 is relay define,don't change them.
You only need to change the RB0~RB3/RC0~RC3 value.


Before 'current calibrate', you need to goto 'measurment'->'curve tracer',check the 'calibrate before measurement' and click the "Offset test" button. so that system will calibrate again and use the new calibrate parameter on follow-up measure.

And goto 'Calibration->Current calibrate',use a wire connect sock B and C,and check the 'RB1=6K' and 'RB2=91K' and 'RC3=12K' then click 'Calibrate' button,
system will use the RB1/RB2/RC3 as 'reference resistor' to calibrate another resistor, and then click the 'save' button.
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Old 8th May 2012, 02:40 PM   #153
NicMac is offline NicMac  Italy
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Thanks locky_z!
Just what I needed to know.
Nic
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Old 9th May 2012, 08:31 PM   #154
NicMac is offline NicMac  Italy
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locky_z,

More questions.....
When the software calculates a value from a curve you say it does so by "linear interpolation". As the curves are not linear I think you are only using the nearest measured values (above and below) to define the line. Is this correct?

I am trying to understand how to make the most accurate and reproducible measurements (Id/Vgs at fixed Vce for mosfets). I think this is best achieved by altering the number of "V steps" and "AD sample" times. Do you have any suggestions?

The accuracy is already very good, but I would hate not to maximize it.

How can I transfer the data (raw traces and sorted values) from your software to Excel. Is there some kind of export function? I cannot copy the DUT ID from the sorted data.

Thank you,

Nic

Last edited by NicMac; 9th May 2012 at 08:43 PM.
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Old 10th May 2012, 01:45 AM   #155
locky_z is offline locky_z  China
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Quote:
Originally Posted by NicMac View Post
locky_z,
More questions.....
When the software calculates a value from a curve you say it does so by "linear interpolation". As the curves are not linear I think you are only using the nearest measured values (above and below) to define the line. Is this correct?
The system uses 'the least squares method', fitting a straight line based on the given interval data
You can find 'the least squares method' algorithm in Excel.

Quote:
Originally Posted by NicMac View Post
I am trying to understand how to make the most accurate and reproducible measurements (Id/Vgs at fixed Vce for mosfets). I think this is best achieved by altering the number of "V steps" and "AD sample" times. Do you have any suggestions?
The ‘v steps’ will not make more accurate.
The 'AD sample' may make more accurate,but measure time may long,so the temperature of DUT may increase, mean the begin temperature of curve is different with the end temperature of curve.

Quote:
Originally Posted by NicMac View Post
How can I transfer the data (raw traces and sorted values) from your software to Excel. Is there some kind of export function? I cannot copy the DUT ID from the sorted data.
Nic
On any tabular data,you can right click, and select copy to clipboard, and then goto to EXCEL, paste the data.
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Old 10th May 2012, 04:51 PM   #156
NicMac is offline NicMac  Italy
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Thank you locky_z!

Quote:
Originally Posted by locky_z View Post
The system uses 'the least squares method', fitting a straight line based on the given interval data
How does the software determine on which interval to apply the least squares method?
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Old 11th May 2012, 12:54 AM   #157
locky_z is offline locky_z  China
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Quote:
Originally Posted by NicMac View Post
Thank you locky_z!


How does the software determine on which interval to apply the least squares method?
When you hold down mouse left button and draw a rectangle, system will popup a menu , then you can choice 'X-axis range' or 'Y-axis range' calculate.
The least squares method is base on the rectangle range.
It calculate the 'line slope' and 'R2'(what is mearn 'R2' please look for EXCEL).


The system units of measurement all is mA & V.
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Old 11th May 2012, 03:02 AM   #158
carpin is offline carpin  Netherlands
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Tektronix Measurement Concepts

About curve tracer measurements

Semiconductor Device Measurements
http://www.slack.com/TE/TekConcepts/...vMea_Apr69.pdf


Tektronix "Concepts" Series Books
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Old 14th May 2012, 12:47 AM   #159
locky_z is offline locky_z  China
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Quote:
Originally Posted by NicMac
I am measuring mosfets at:
constant Vce 16V, Imax 2600 mA
VB 1.5-3
RB 91K
RC 4.55R
Sometimes the traces are interrupted (current goes to zero) before I reach 2500 mA. Why is this? The current limiting circuit?
Can I increase this to 3500-4000 mA safely without danger for the instrument?
What are the critical components I could/should change?
Nicolai
There are two reasons when the traces are interrupted.
1. Over-current protection is not to enter the protected, and ‘Imax’ set equal to 2500mA, the measuring current reach or more than 2500mA,it will normal suspension of. and traces show normal.

2. When close to the measurement socket next to the LED light, it mearn the circuit into the over-current protection status. it were suspended. The last point of the curve measured values ​​will produce abnormal. and last point on the traces show abnormal.

The curve tracer can measure more than 4A current safely.
Increase the over-current point ,you can replace the green resistor on picture
Click the image to open in full size.
but the resistor value you need to try.


Or install a tact switch on ProtectSW near the measurement socket. when you press the switch ,the over-current circuit not work,so it can measure no limit current, and board have no protect.(I don't suggest)
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Old 17th May 2012, 06:47 AM   #160
NicMac is offline NicMac  Italy
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Quote:
Originally Posted by locky_z View Post
but the resistor value you need to try.
I will try. Any suggestions for starting values?
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