Fluke Biomedical 943-25 - Manual (Page 17)

Maintenance, Calibration, and Troubleshooting
Commercial Detectors
4
4-5
Table 4-2. Recommended Test Equipment
Feature Specification
Pulse Generator (Square Wave)
Pulse
± 0.1 to 5 V variable (into a 50 ohm load)
Rise Time
≤ 30 ns
Pulse Width 1.0 microsecond (variable)
Output Impedance 50 ohms
Maximum Repetition Rate 2 MHz
Digital Voltmeter
Ranges
± 0 to 100 mV up to ± 0 to 1000 V (20%
overrange)
Accuracy ± 0.1% of input +1 digit
Input Impedance
≥ 10 megohms
Oscilloscope (Dual Trace)
Bandwidth 10 MHz @ 10 mV/div
Fastest Sweep Time < 10 Microseconds/div
Electrostatic Voltmeter
Range 0 to 2000 VDC
Precision
± 1%
Input Impedance 10 12 ohms
Counter/Scaler
Maximum Count Rate 10 5 cps
Minimum Pulse Width for Counting 40 ns
Preset Counting Time 0.1,1.0, and 10 minutes
4.7.2 Dynode Test Measurement
Preamplifier input is easily damaged. Ground pin 3
of Z1 before applying power and measuring
photomultiplier tube anode or dynode voltage.
1. Using an electrostatic voltmeter, measure the total DC resistance of the dynode string. The value
should be 9.67 megohms ± 15%. If no reading is obtained, check dynode resistor interstage
connections.
2. Connect the cable to the readout.
3. Turn on channel power and apply 900 V to the detector. Measure the anode resistor voltage (R13)
using an electrostatic voltmeter. The value should be 900 V.
4. Remove channel power.
4.7.3 Preamplifier Checkout
High voltage must be removed for this test.
1. Remove the grounding jumper from pin 3 of Z1.
2. Connect an oscilloscope to the input circuitry of the readout (50 ohms terminated).
CAUTION