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1.0 Introduction
1.1 Handling Scientifica equipment – precautions
This section contains important safety information related to general use of the Scientifica
MDU. The MDU is a piece of scientific equipment and as such requires care when handling.
Adjustment or removal of any screws or components other than those noted in
this manual can adversely affect the performance and operation of your device and
may invalidate your warranty.
High Voltage Hazard Warning
The PMTs in the detector modules operate with voltages of up to -1000 V. Whilst the detector modules are
closed, there is no risk to the user from these voltages, but a serious risk to health might occur should the
module be opened and the safety interlock defeated.
Please do not open the detectors!
PMT Over-drive caution
The preamplifiers integrated within each detector module have sufficient gain in most cases to saturate
(generate full-scale output signal) well before the PMT delivers its maximum safe output current. The data
acquisition system can be set up to saturate before full-scale signals are attained. Some detector variants
may be fitted with an average output current trip circuit that cuts power if dangerous signal levels are
encountered. Prolonged operation above, or near the maximum, rated current output will damage the PMTs or
give rise to excessive noise.
PMT Over-exposure caution
PMTs operate best when kept cool, under power and in the dark! Exposure to bright lights can lead to
damage and reduced sensitivity, as well as excessive noise. The system is designed to prevent accidental
exposure to bright lights and to cut off the high-voltage should this possibility arise. Do not attempt to defeat
the safety interlocks or to disassemble the main optical block. Make proper use of the “master safety”
switch on the controller and move the laser / visible dichroic mirror to the “safe” (withdrawn) position whenever
working on the microscope with the lights on.
To prevent inadvertent damage to the PMTs, the system incorporates various safety features: the PMTs are
cut off whenever the laser dichroic mirror is withdrawn from the beam, and as a secondary precaution the
optical path is blocked by a mechanical shutter which keeps the detectors dark and maintains their noise at a
low level. In addition, the PMTs are cut off whenever the filter cube is removed. Lastly, the controller has a
“master safety” switch which can disable both detectors when the preparation is to be viewed under
conventional illumination or during setting up.
Environmental conditions caution
If the system has been stored in a cold place and is suddenly brought into contact with warm air, condensation
may form. This will “fog” the optics, but it may also affect the high-voltage supplies in the detector modules. A
cold system should be allowed to equilibrate to room temperature before operation (which may take a few
hours in some cases).
The detection system should not be operated at humidity levels exceeding 80% or if there is any risk of
condensation.
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