Introduction
The PDA-750 is a low noise, high gain transimpedance amplifier that is designed to provide a direct
digital readout of the current generated from a photodiode, photomultiplier, or other similar current
source. With full scale input ranges of 20 nA to 20 mA and a noise level of less than 1 pA, the PDA-
750 offers superb dynamic range.
Digital selection of a calibration factor in terms of Amps/Watt via the front panel controls permits
the unit to display the measurement directly in terms of Watts. The A/W setting may range from
1.000 to 0.100 in .005 steps. Subsequent current readings are divided by this cal factor when the
Amps / Watt control is engaged.
A variable bias voltage ranging from +14 V to -14 V may be digitally selected from the front panel
and applied in series with the photodiode under test. The background cancellation feature allows
offsets of from +100 % to -100 % of the selected full scale range to be added or subtracted from the
input signal.
Rechargeable batteries isolate the unit from the mains and eliminate the effects of ground loops
and/or power line noise. They will provide power to the unit for a minimum of 10 hours of opera-
tion between charges. The unit may be operated normally while the batteries are charging.
The large 4 1/2 digit Liquid Crystal Display provides a maximum resolution of 1 part in 20 000 thus
permitting the detection of very small changes in the variable that is to be measured.
An analog output is provided with a 2 volt full-scale signal that is proportional to the maximum
display reading of 20 000 counts. Applications for this unit include; serving as a readout for
Unity Quantum Efficient Detectors such as those manufactured by UDT Instruments, character-
ization of detector dark current, spectral calibration of detectors, and use as a sensitive, low cost
optical power meter.
The instrument may be controlled and interrogated by means of its built-in bi-directional Rs-232
serial port.
All settings are retained in non-volatile memory so that the user need not reset all values when the
unit is turned back on.
Unpacking and Inspection
Prior to shipment this instrument was inspected and found to be free of mechanical and electrical
defects. Upon acceptance by the carrier he assumes responsibility for its safe arrival. After unpack-
ing, examine the unit for any evidence of shipping damage. Should you receive this instrument in a
damaged condition, apparent or concealed, it must be noted on the freight bill or express receipt and
signed by the carrier’s agent. Failure to do so could result in the carrier refusing to honor the claim.
Upon filing a claim TTI should be notified.
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