keita.kawabe@LIGO.ORG - posted 13:39, Tuesday 15 August 2023 - last comment - 20:52, Wednesday 16 August 2023(72241)
OM2 Beckhoff cable disconnected, voltage reference is used as a heater driver input
As a followup of alog 72061, a batter-operated voltage reference was connected to the OM2 heater chassis. Beckhoff cable was disconnected for now.
Please check if the 1.66Hz comb is still there.
Beckhoff output was 7.15V across the positive and negative input of the driver chassis (when the cable was connected to the chassis), so the voltage reference was set to 7.15V.
We used REED R8801 because its output was clean (4th pic) while CALIBRATORS DVC-350A was noisy (5th pic).
detchar-request git issue for tracking purposes.
As you can see from one of the pictures above, the unit is powered with AC supply so we can leave it for a while.
How to recover from power outage
If there is a power outage, the voltage reference won't come back automatically. Though I hope we never need this instruction, I'll be gone for a month and Daniel will be gone for a week, so I'm writing this down just in case.
0. Instruction manual for the voltage reference (R8801) is found in the case of the unit inside a cabinet where all voltage references are stored in the EE shop. Find it and bring it to the floor.
1. The voltage reference and the DC power supply are on top of the work table by HAM6. See the 2nd picture in the above alog.
2. The DC supply will be ON as soon as the power comes back. Confirm that the output voltage is set to ~9V. If not, set it to 9V.
3. Press the yellow power button of the voltage reference to turn it on. You'll have to press it longer than you think is required. See the 1st picture in the above alog.
4. Press the "V" button to set the unit to voltage source mode. Set the voltage to 7.15V. Use right/left buttons to move cursor to the decimal place you'd like to change, and then use up/down buttons to change the number.
5. Most likely, a funny icon that you'll never guess to mean "Auto Power Off" will be displayed at the top left corner of the LCD. Now is the time to look at the LCD description on page 4 of the manual to confirm that it's indeed the Auto Power Off icon.
6. If the icon is indeed there (i.e. the unit is in Auto Power Off mode), press power button and V button at the same time to cancel Auto Power Off. You'll have to press the buttons longer than you think is required. If the icon doesn't go away, repeat.
7. Confirm that the LCD of R8801 looks exactly like the 1st picture of the above alog. You're done.