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HP 53131A HELP
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samson:
Hi, I have the HP 53131a Frequency counter with the genuine HP 010 med oven oscillator fitted. My question is if I take the HP 010 out of the unit and bench calibrate it against a 10mz gpsdo and connected to a oscilloscope ,I can adjust the trim pot so it is exactly 10mhz. When put it in the HP010 back into the counter and do a time base calibration is comes up as failed. To fix this I have to turn the trim pot on the HP 010 oscillator out of the 10mhz zone and do the test again and it will pass the test. Is this because the algorithm its to far off for the it to make the adjustment.? and why do they put the trim pot there.
The other question is when the HP 53131a comes from the factory fitted with 010 oscillator does it still have the on board oscillator at the back of the unit or do they omit this.
Any help or advice appreciated
SCSKITS:
When you bench calibrate the HP oscillator against your reference timebase, did you set the electronic frequency control input on the oscillator to mid range?
If not, the mechanical adjustment may get you to 10MHz but be out of range for the electronic calibration as the input will be set all the way to one end.
ed.
Tony_G:
You don't need to take it out of the 53131A unless you want to use it for some other reason - They're designed to be calibrated in place.
The procedure is documented in the Service Manual on page 2-24:
--- Quote ---To Calibrate the High Stability Timebase Option (Medium, High,
or Ultra-High)
NOTE Allow the Counter to warm up for approximately 24 hours before performing
this calibration. This calibration is unlikely to fail, unless the Counter is not warmed
up.
1 Connect the output of a 10 MHz house standard to Channel 1 of the Counter as
shown in Figure 2-5.
2 Press any one of the arrow keys until CAL: TIMEBAS? is displayed.
Note that the timebase choice (CAL: TIMEBAS?) only appears when the Timebase
Option is installed.
3 Press Enter key and follow the instructions in the scrolling message that appears
in the Counter display.
4 Press Enter key after each instruction.
The Counter displays CALIBRATING, and then it should display TB CAL PASS.
If the fail message is displayed (even after the Counter has been warmed up for 24
hours), refer to the troubleshooting section in this chapter.
This completes the High Stability Timebase Option Calibration procedure.
If all tests passed, the Counter is now calibrated.
--- End quote ---
TonyG
SCSKITS:
To get to the calibration menu, you have to press the Scale & Offset key while turning power ON.
Then press the Scale & Offset key until CODE: is displayed.
Then you can access the menu list.
Use the arrow keys to get to the timebase cal menu item as mentioned in the previous post.
At this point, wait for the timebase to warm up, the longer the better.
I usually run it at this point over night so I do not have to cycle power after the oven is warm.
If you want, you can connect the 10MHz reference to the counter channel A input and watch the warmup as the counter display approaches 10.000000,0MHz.
Note: early versions of the counter do not access the menu in the above manner.
The CAL menu is accessed through the UTILITY menu.
Also there is no security on the CAL menu in older units.
ed
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