Fluke Biomedical 945A - Manual (Page 39)

Victoreen Communications Loop
Communication between the detector preamplifier and the UDR is performed via a Victoreen loop, a
serial asynchronous communications interface. The communication utilizes Victoreen protocol and is
intended for use in electrically hostile environments where high noise immunity is required. Noise
immunity is achieved using differential line driving, and electrically isolating the end of each
transmit/receive pair with opto-isolators. Using a ±15 Vdc communications power supply, each 0 to 1
transition is equivalent to a 30 volt swing in loop voltage. Refer to the Model 942-200-80-1
Communications Board instruction manual located in Appendix A for further information.
Preamplifier Switch & Jumper Settings
Switch and jumper settings for the preamplifier are summarized in Table 4-3, 4-4, and 4-5.
Table 4-3. Preamplifier Interface Board 977-210-10 Switch Settings
Switch Normal Op. Switch Function
SW3-1 ON 0/OFF Selects 300 baud • 1/ON Selects 4800 baud (normal setting)
SW3-2 OFF 0/OFF Selects alarm inhibit, SW3-3 must be on for this state to be true.
1/ON Selects alarm enable
SW3-3 OFF 0/OFF Selects Rate Mode (normal) • 1/ON Selects Maintenance Mode
SW3-4 OFF 0/OFF forces 977 analog output to 0 V (low scale)
(SW3-3 must be on for state to be true)
1/ON forces 977 analog output to 10 V
(SW3-3 must be on for state to be true)
NOTE
The above switches are located in a 4 position dip switch on the
977 interface board (977-210-10).
Table 4-4. Jumper Positions for Preamplifier Interface Board 977-210-10
Jumper Normal
Setting
Function Alternate
Setting
Function
JMP1 A to B Enables Victoreen Loop (normal) B to C Enables RS232C
JMP2 N/A Deleted, Not Used N/A Deleted, Not Used
JMP3 A to B Enables Alarm Output -
Non-Failsafe B to C Enables Alarm Output
Failsafe
JMP4 A to B Enables 0 - 10 Vdc Analog Output
(normal) B to C Disables Analog Output (stays at
10 Vdc)
JMP5 B to C Enables HV Output (normal) A to B Disables HV Output
Table 4-5. Jumper Positions for Preamplifier Electrometer Board 977-200-15
Jumper Normal
Setting
Function Cal.
Position
Function
JMP1 A to B Normal Operation B to C PGA Offset Adjust *
* Programmable Gain Amplifier
4-15