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A modern single-channel photometer

Next, consider a more modern photometer that uses pulse-counting. It has a ``neutral'' filter in addition to standard uvby filters. The ``neutral'' filter is in series with the passband filters, and is used to determine the dead-time correction. The positions of these two filter mechanisms are recorded as two adjacent digits in the data, so we can treat them as a single filter code; the second digit is 1 when the ``neutral'' filter is in the beam.

There is also a shutter whose position is encoded separately in the data stream: 0 means open, 1 means shut. This can be treated as a second logical filter mechanism.

The photomultiplier in this modern instrument is in a thermoelectrically cooled chamber, regulated to run at $0^{\circ}$ C (273 K). Table I.14 shows what we get.

Again, there is only one detector, so we need not include the NDETUSED column.


 
Table: Instrument table file for a two-channel photometer
Descriptor values:

NFILTCAR = 2

NDETS = 2

FILTSTAT = MEASURED

FILTCAT = ' ' (blank string)

CONDITION = AVERAGE

Passband sub-table
NBAND BAND FILTCODE_1 FILTCODE_2 REDLEAK NDETUSED
--- -- ----- ----- ---- ----
1 U 1 any BLOCKED 1
2 B 2 any BLOCKED 1
3 V 3 any ABSENT 1
4 R any 1 BLOCKED 2
5 I any 2 ABSENT 2
6 DARK1 0 any   1
7 DARK2 any 0   2

Detector sub-table
NDET DET SNUMBER MODE COOLING
-- -- ---- -- ----
1 PMT S-13 CI MEASURED
2 PMT GAAS CI DRYICE

 


next up previous contents
Next: A modern two-channel photometer Up: Sample instrument files Previous: A simple photometer
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1999-06-15