This module consists of eight independent sample-and-hold
amplifiers. These amplifiers retain the maximum signal (final integrated value)
produced by the input amplifier for each filter position. The system can
support up to four independent input modules (A B C and D), although no more
than two (usually A and B) would normally be required. The output module is
normally configured to operate with either the A or the B input module (or some
combination of the two), and two output modules can be used at the same time.
There is also a provision to accept signals from the C and D input channels if
required. The outputs from the sample-and-hold amplifiers are available on the
front panel, and they can also be sent to other modules via signal lines on the
system backplane. For each of the eight amplifiers, there are two such signal
lines available, each designated A and B to match their intended source. There
are thus sixteen output data lines altogether, labelled A1-A8 and B1-B8
respectively. However, some additional configurations are possible as described
below.
Associated with each sample-and-hold amplifier is a signal input, a control input and a signal output. The amplifier samples the input signal when the control input is high, and retains the latest input signal when the control signal goes low. The control signals are generated by circuits in the main system enclosure. The digital control board within the enclosure has a jumper link that can be set to produce control pulses appropriate for rotors with two, three, four, six or eight filters. The normal configuration is six filters, which leaves two spare amplifiers in the output module; however, these can still be used under some circumstances.
Selection of the input signals for the output amplifier is normally made between the A and B input amplifiers; however, the signals from the C input amplifier (if fitted) can be selected in place of the A input amplifier by jumper bank J1, and a similar substitution of D for B can also be made. These two substitutions can be made independently, but they affect all the sample-and-hold amplifiers together.
Each amplifier has a jumper link to select whether its input is connected to the A or B input signal (which may have been diverted to C or D as described above), and these are grouped together as jumper bank J2. For normal operation these jumpers should be connected to the A signal line, and this is the normal factory configuration.
Jumper bank J3 independently connects the outputs of amplifiers 1-8 either to the A or B output signal line for that filter position (note that there are no corresponding C and D output lines on the system backplane). The operation of this jumper bank is exactly as for J2, and the normal setting is to the A lines.
Jumper banks J4 and J5 provide additional output configurations which may be of use under some conditions.
Normally the pairs of pins comprising J4 are not connected, but if the shorting links for positions 5-8 on J3 are removed and replaced on the corresponding links of J4, then the effect is to connect sample-and-hold amplifiers 5-8 to output lines B1-B4 respectively. Of course, this would normally place the outputs for filter positions 5-8 on these lines, but jumper bank J5 (sampling diversion) can be reset to make these sample-and-hold amplifiers accept the signals for filter positions 1-4 instead. This is intended to allow one output module to provide all the outputs for two photodetectors, when the rotor has four or fewer filter positions. In this case, the 1A-4A signals are available on output sockets 1-4 and are sent to the 1A-4A lines on the system backplane. The 1B-4B signals are available on output sockets 5-8 and are sent to the 1B-4B lines on the system backplane.
Jumper bank J5 also allows decoding of four filter positions from four input amplifiers when two output modules are used. In this case, J5 on both output amplifiers would be set to divert the sampling of amplifiers 5-8 to filter positions 1-4. In a typical configuration, J1 of the first output module would be set in the normal position, whereas J1 of the second output module would be set to select the C and D inputs instead of A and B. Output sockets 1-4 of the first output module would then carry the four decoded A signals, and sockets 5-8 would then carry the four decoded B signals. These eight signals could also be made available on backplane lines A1-A8. Similarly, output sockets 1-4 of the second output module would carry the four decoded C signals, and sockets 5-8 would carry the four decoded D signals, with all these signals also available on backplane lines B1-B8.
Many other configurations are also possible, so please contact us for advice if your requirements are not met by any of the examples discussed here.
