User manual
ADDENDUM
Below is a wiring diagram showing a remote RM-60 connected to computer’s serial port by way of 5000 feet of cable using
only two leads. Since we have plenty of power from external power supply, we added a 1.2K ohm pull-up resistor. The pull-
up resistor in RM-60 is 4.7K ohm, limited by the small amount of power available from computer’s serial port. The additional
pull-up resistor will add to the extreme noise resistance. A hefty silicon transistor inside the RM-60 (KN3904) pulls the signal
line to negative with each count. It can dissipate 400 mw.
As regards the power supply, a good +9VDC, -9VDC power supply will work. These cost about $45. If you locate the power
supply by the computer, and run an additional two wires out to the RM unit(s) to carry the +9VDC -9VDC, or if you use a
lower quality power supply, you should add power supply filter caps. out by the RM unit(s). Two filter caps should be added,
one between +9 and ground and one between -9 and ground. Use a cap. with good high frequency response for good slew
rate, for example, 25 volt, 10 mfd. tantalum caps, or a combination of a smaller mfd. tantalum cap. and a 10 to 100 mfd
electrolytic cap.
Current draw by each RM unit will be perhaps 2 ma, but with extremely high radiation levels, this could reach perhaps 10
to 20 ma. Instead of a power supply, you could use two 9 volt batteries to supply the power, along with the filter caps. as
described above.
As regards cabling locations with multiple RM-60s,70s,80s,etc., you could connect all signal ground leads from multiple ports
together so that each RM-monitor shares the same signal ground lead, allowing the use of only one additional wire for signal
per RM-monitor so that, for example, 4 monitors would need a cable with 5 leads, namely four signal leads and one signal
ground.
The serial ports meet RS-232 specs. so have built in safeguards. You could add a 26 volt MOV surge protector between signal
ground and each lead from port. You might want to add a "TrippLite" "ISOBAR" surge suppressor, with 21 active electronic
filtering components ($49.90) or a "TrippLite" battery backup system which includes the filtering components ($250), to your
computer’s power line. IF YOU HAVE ANY QUESTIONS, PHONE US.
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