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G-7901D Telemeter FS Transmitter
G-7902C FSK Receiver
G-7903B&C Analog Multiplexers

The G-7901D and G-7902C telemetry system provides higher accuracy and greater temperature stability than conventional telemetering systems. These features stem from the extensive use of crystal stabilized oscillators for frequency synthesis and detection circuits. Typical telemeter converter accuracy is better than 0.1% over a temperature span of 0 to 50 degrees C.

The G7901D Telemeter, FS Transmitter linearly converts a dc voltage or current to a subaudio frequency in the ranges of 10 to 30, 5 to 15, 18 to 30, and 5 to 25 Hz. This subaudio frequency modulates as on-board frequency shift(FS) transmitter to produce narrow band FS signals in a range between 420 Hz and 10 kHz. These signals can be transmitted over standard, voice-grade telecommunication channels such as telephone wires, microwave or optical fibers. The output filter of the transmitter exhibits 600 ohms nominal with rising impedance out of band to allow frequency multiplexing of several transmitters onto one transmission medium.

The input to the telemeter converter may have spans in the range of 100 mV to 10 V with 0.0 V at left scale or within the span. The differential input is provided to allow the user to drive the telemeter with out concern for ground placement. This differential input exihibits an input impedance exceeding 1 megohm per volt. An on-board calibration network with front panel switch allows the user to move from the operation mode to the calibration mode to tune the telemeter response. The calibration network typically allows left, center and right scale user calibration.

The output of the differential amplifier on the calibration network drives the scaling amplifier. The scaling amplifier is calibrated such that when the left scale and right scale voltages are input, the output of the voltage-to-frequency converter is subaudio or moduation frequency required. The voltage-to-frequency converter then keys the two-frequency transmitter at the subaudio rate. A solderless jumper selects either a 10-30 Hz or 5-12 Hz subaudio tone rate.

An optional relay can be provided on the G-7901D for retansmission of the subaudio frequencies, alowing a second FS transmitter to be keyed. Plug-in filter sections are also available.

Specifications

DC Input Span: 100mV to 10 V ranges standard, custom ranges available from factory. Input Impedance: Greater than one megohm without current shunts. Modulation Frequency: 10 to 30 Hz standard; 5 to 15 Hz and others available. Accuracy: 0.15% from -5 degrees C to +55 degrees C. Linearity: 0.015% of full span. Response Time: Left scale to right scale in less than 100 ms. Temperature Stability: Better than 0.005% per degree C from -5 to +55 degrees C range. Operating Temperature: -5 to +70 degrees C. FS Tranmitter Stability: 0.15% +/- 2 Hz in temperature range of -5 to +55 degrees C. Output Levels: -25 to 0 dBm, adjustable. Squelch: +3 to +25 Vdc turns off tones. Output Filter: Rising impedance out of band characteristics, coils soldered in with plug-in filter section available. Power Requirements: +12 V supply, 46 mA; -12 V supply, 24 mA.

CRYSTAL OSCILLATOR CONTROLLED WIDE TEMPERATURE OPERATION 0.15% ACCURACY DIFFERENTIAL INPUTS BUILT-IN CALIBRATION NETWORK OPERATION INDICATOR OPTIONAL UNIVERSAL PLUG-IN FILTER

DataSheet: G-7901D.pdf  10-01-03  36KB

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