DVM

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[edit] Introduction

"DVM" refers to the Agilent 34970A Digtial VoltMeter Media:Agilent34970A.pdf‎ which is used in Radon EDM experiments. The DVM has 22 channels and can read out voltages, currents, resistences or frequencies. These values are sampled every 2 seconds and sent to the mlogger independant of run starts and stops. The event type for this frontend is "8" and the bank name used is "DVM0". The values are all floats.

[edit] Starting/Rebooting

To start the DVM frontend:

  • Log into lxdaq02 using the eightpi username
  • Move to the folder /tig/grsmid00_home1/eightpi/online/DVM
  • Type the command ./DVM
  • Some initalization statements are written to the terminal
  • Normal cycling of the frontend will print out the (non-zero) values of the 22 channels every 2 seconds
  • If a channel reads out exactly zero then it is most likely not initiated, #Adding/Removing Channels

[edit] Stopping

To stop the DVM frontend click on the "programs" button at the top of the MIDAS status page and then click the "Stop DVM" button on the right-hand side.

[edit] Current Channel Configuration

The current configuration of the DVM channels. Last updated 13th August 2008.

Channel Type Name
1 DC Voltage Hall Probe X (1 Volt/Gauss)
2 DC Voltage Hall Probe Y (1 Volt/Gauss)
3 DC Voltage Hall Probe Z (1 Volt/Gauss)
4 DC Voltage Coldfinger Temperature
5 DC Voltage Empty
6 DC Voltage Empty
7 DC Voltage Empty
8 DC Voltage Empty
9 DC Voltage Empty
10 DC Voltage Empty
11 DC Voltage Empty
12 DC Voltage Empty
13 DC Voltage Empty
14 DC Voltage Empty
15 DC Voltage Empty
16 DC Voltage Empty
17 DC Voltage Empty
18 DC Voltage Empty
19 DC Voltage Empty
20 DC Voltage Empty
21 DC Current Empty
22 DC Current Empty

[edit] DVM Source Code

The source code for the DVM frontend is located in /home/8pi/online/DVM/frontend.c

[edit] Adding/Removing Channels

There is a maximum of 22 channels. Channels 21 and 22 can only read AC or DC current values. Channel numbers start at one and are offset by +100 ie. channel 4 is 104. Only channels which are initalized in the frontend code will read out.

Channels 1 to 11 are initalized to read DC voltages with these two statements in the frontend_init() function of the #DVM Source Code:

  • rs232_puts(hDev, "CONF:VOLT:DC AUTO,MAX, (@101:111)\r\n");
  • rs232_puts(hDev, "ROUT:SCAN (@101:111)\r\n");

To change what channels are read out, modify these statements appropriatly. To alternatively read a temperature from channel 3 use:

  • rs232_puts(hDev, "CONF:TEMP RTD,85,(@103)\r\n");

[edit] If all channels read zero

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