User Guide ...
This page offers a brief outline of operating the detector and a few troubleshooting tips should problems arise. A full guide in pdf format can be found in the downloads section.
Operating the detector is quite simple and is done via the switches on the circuit board which is mounted on the side panel. The uppermost switch is for the audible beeper which is best left in the off position because it's quite loud.
Below this is a 3-way switch that controls the signal processing. In the upper position, the counter will only consider the signal from tube #1, centered it requires a coincidence from both tubes to trigger a count, and in the lower position it only considers the signal from tube #2. This is useful for checking the signal from each tube independently and demonstrating the coincidence principle.
To the right and below the signal switch is the 3-way counting switch. In the upper position it will run the counter indefinitely until it is centered in the count hold position or power is interrupted. In the bottom position it will initiate a timed count which will count uninterrupted for the set duration and then hold the count on the display. The count duration is adjusted via the screw on the potentiometer. While counting, the green counting LED will be illuminated near the display.
The switch in the lower right corner of the board is used to clear the display. In the upper position it will display the counted coincidences on the red LED display. Toggling the switch down will force the display to "000" and it will be unable to count until it's returned to the top position.
Electrical connections to the board are made via corresponding MOLEX 2-pin headers on the left side of the board.
A photo of the LBL-style circuit board is shown below with labels for the switch positions and header connectors.
Operation and Troubleshooting ...
Counts are taken by plugging in the AC adapter into the wall and connecting it to the plug on the case. The display digits will light up and display a random pattern. Clear the display with the switch so it reads "000". Select the center position on the signal switch to count coincidences and then select either count infinite or timed count. The green LED will light up and the displayed count will increase accordingly. To stop the count, just move the count switch to the center position (a timed count will continue for the duration and then hold).
One common bug with the CRD is a failure to count when the detector is on. This is probably due to a bad or loose connection to one of the PMT signal wires. Use the signal switch to check both tubes separately; they should count very quickly individually. You can also try jiggling the header connectors and the count should resume. Unfortunately, jiggling the signal wires can create noise which could lead to false counts.
If at any time the display flickers or fails to illuminate, this is due to either a faulty voltage regulator or AC-DC transformer and should be tested and replaced as soon as possible. Any thing over 12 volts DC into the circuit board could overload the regulator and cause more than the recommended 5 volts for the PMTs causing damage to the electrodes. |
