Detection Electronics
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The
200 Series is a modular system of signal processing electronics which
aims to provide a computer interface for all the optical detectors used
in light measurement systems.
This range of GP-IB programmable units allows the user to configure high quality dc and lock-in amplifiers with current voltage inputs to suit all optical detectors. An optical chopper, high voltage supply and programmable relay/utility module can also be included to provide an "all-in-one box" optical detection system which is equally at home in one of our spectroradiometers or as a general purpose laboratory instrument.
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200 Series Modules
| 215 | High voltage power supply | An
ancillary unit which provides a source of high voltage for
photomultipliers and photoconductors such as lead sulphide. The
output voltage can be monitored on the 217 display and set using a front
panel screwdriver operated adjustment. The unit can be switched
off independently from the 217 bin by a front panel toggle switch or
remotely by contact opening.
Output: -300V to -1500V at 2mA Stability: 100ppm/K
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| 218M | Optical chopper with modular control electronics | The
218M is the control electronics for our ever popular 218 chopper in
modular form. Four easily interchangeable chopping discs are
provided as standard which allow chopping frequencies in the range of
0.5Hz to 3kHz. The chopping frequency is indicated by the a
digital indicating dial and a squarewave reference output for use with
lock-in amplifiers is provided.
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| 225 | Lock-in amplifier for use in chopped light systems | A
GP-IB programmable lock-in amplifier which features dual inputs and
squarewave demodulation. The high impedance input is ideal for
connection to photoconductors. Two-phase or multi-channel lock-in
systems can be assembled using two or more 225s in a single 217 bin.
Frequency range: 0.5Hz to 100kHz (-3dB) Input impedance: 100MW/30pF Sensitivity range: 1mV to 1vrms for 10V DC output Time constant: 10ms to 10s
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| 228A | Integrating A to D converter | This
takes the analogue output from the 225 or 267, digitises it, and passes
the result to the computer. Unlike some A to D's, the 228A makes
full use of the available signal information. At the end of the
100ms conversion, the digital output represents the true average of
analogue input during the period. As the unit is free-running, no
information is lost when multiple conversations are performed. The
allows the use of digital averaging in place of the usual analogue time
constant and the use of variable averaging periods to give constant
signal-to-noise as signal levels change.
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| 262 | Programmable relay/utility module | A
general purpose GP-IB (IEEE488) programmable relay unit that
incorporates 8 programmable relays grouped into 2 sets:
Signal switching: 4 relays, each with an individual BNC input socket and a common BNC socket; Utility switching: 4 independent single-pole changeover relays each with its own front panel indicator; Trigger: a single input is included which enables an external switch the be sensed over the GP-IB, i.e. to begin a measurement.
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| 267 | DC current amplifier (electrometer) for use as a main amplifier in DC systems using current source detectors | This
is used as the main amplifier in DC systems employing photodiode or
photomultiplier detectors. At low frequencies, such devices give
their best performance when connected to this type of virtual ground
input current amplifier (see also 277). Programmable dual inputs
allow the use of pairs of detectors to increase the wavelength range of
a scanning system. Typical examples include pmt/Si, Si/Ge, and SI/InGaAs.
Transconductance: 10E10 V/A to 10E5 V/A Bandwidth: DC to 30Hz
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| 275 | Ultra
low noise voltage pre-amplifier for use with mercury cadmium telluride
detectors
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The
input voltage noise of this unit is less than that produced by a 50W
resistor at room temperature. The 275 has been designed
specifically for use with mercury cadmium telluride detector.
Special features include an input shorting switch to avoid damage to the
detector during connection and a constant current biasing circuit which
allows you to set precisely the bias current recommended by the detector
manufacturer without having to select resistor values.
Frequency range: 0.5Hz to 100kHz Voltage gain: x500
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| 277 | Pre-amplifier
for use with current source detectors in chopped light systems
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For
optimum linearity and signal to noise performance, photovoltaic
detectors should be used with zero ohms load. The virtual ground
input of the 277 achieves this condition while providing an output
voltage proportional to the detector current. The programmable 6
decade sensitivity range, in conjunction with the 225, allows the user
to choose a combination of current and voltage gain which optimises the
trade-off of noise performance versus DC current sinking. The dual
inputs can be used with detectors of the following types:- Si, Ge,
InGaAs, InSb and photomultipliers.
Transconductance: 10E3 V/A to 10E8 V/A Bandwidth: DC to >5kHz on all ranges
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| DH-Py | Power
outlet for DH-Py detector head
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218 Optical Chopper
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A free-standing control unit
coupled to the chopping head. Four easily-interchangeable chopping
discs are provided as standard which allow chopping frequencies in the
range 0.5Hz to 4KHz.
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