Products > Test Equipment
Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)
joeqsmith:
Half hour should be fine. If not, run another half hour. If that doesn't clear them, I wonder how strong the lamp is.
garrettm:
When in doubt, consult the datasheet:
Erasure is a function of light intensity and exposure time. All bits will be "high" after proper exposure. The datasheet suggests around 20 minutes of exposure using a 253.7nm, 12 mW/cm^2 light source with the light placed 1 inch / 2.54 cm above the quartz window.
Exposure is cumulative, so you can periodically read the chip and put it back in the eraser if it didn't finish the first time without harming anything. Though it’s probably better to just leave it in for 30 or 40 minutes to avoid repeated handling.
One extra cycle on a chip that has only been written to once is unlikely to harm its data retention, any more than that and I would be concerned.
garrettm:
I think I know why my setup can't do the high speed reading mode.
When I enable "GPIB talk-back on time out" dip switch on my RS-232 to GPIB converter, I can get the first binary reading back. When I send ? and wait, I can get the next reading. So the HS mode works, but requires the GPIB controller to tell the meter to send data after each ? command.
The problem with the Serial488A is that it can only ask the GPIB device to "talk-back" after a serial termination character (<CR>, <LF>, <CR><LF>, or <LF><CR>) is sent or 100ms after the last serial character (i.e., time out). "Talk-back" using a serial termination sends a GPIB <CR><LF> termination and then the DMM is addressed to talk, which causes the HS reading mode to exit before sending data.
I figure I might have to roll my own controller to get this thing to even come close to that 500 samples/s limit.
And now it's time to see if I can get anywhere close to 240 samples/s in the continuous binary mode...
*A quick update:
Using command string
S0F1R1JT1@<CR>
I can get the meter to automatically send ASCII data at 24-25 readings per second, while
S0F1R1JT@<CR>
gives 18 readings per second. And with
S0F1R1JT1@%Q1@<CR>
I can use the rear trigger to take readings and have them sent to the PC. The max speed of this mode was no more than 21 readings/s with T1 and 15 readings/s with T sampling modes. I didn't see any difference between Q and Q1 triggering while testing.
garrettm:
I found the secret! This may also work for joeqsmith's bit serial interface since he said he received the first binary payload when entering into HS mode.
Since I can't directly put the remote instrument into talk mode, I used the "talk-back on time out" feature of the Serial488A and the Q1 triggering feature to avoid sending ? commands that pull the instrument out of talk mode.
By using an external signal generator I was able to trigger the DMM to 360 samples/s! A new record! However, I have an issue where it pauses on occasion that I need to look into. But I've proven that high speed transfers are possible and might actually achieve the touted 500 samples per second with some massaging.
To test, send
S0JT1@<CR>
%Q1@<CR>
!
and use the external trigger input while monitoring the scan advance.
I assume the serial interface can be tricked into sending binary data using the Q1 trigger as I did with my gimped GPIB bus.
Fast acquisition on the 8505/6A is not a fantasy anymore!
joeqsmith:
--- Quote from: garrettm on February 10, 2021, 07:03:48 am ---.....
And now it's time to see if I can get anywhere close to 240 samples/s in the continuous binary mode...
*A quick update:
Using command string
S0F1R1JT1@<CR>
I can get the meter to automatically send ASCII data at 24-25 readings per second, while
S0F1R1JT@<CR>
gives 18 readings per second. And with
--- End quote ---
With the 607 firmware, the fastest times I have seen using RS232 were using M M1 W Q J P0 X0 U0 S0 F1 B. Basically I'm wanting the meter to do as little as possible. The worse times are around 25ms. Average is about 16ms. Close to 60 readings per second. Graph is showing the time between readings in ms. Histogram is also showing readings per second.
I suspect you will see similar or faster times.
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