AN795 datasheet(6/15 Pages) MICROCHIP

6 / 15 page

AN795

DS00795A-page 6

TELEMETRY

In a telemetry system, the TC9400 converts the analog input (VIN) into frequencies (10Hz to 100kHz) which can be used to modulate

an RF transmitter.

At the other end, a receiver picks up the RF signal and demodulates it back into the 10Hz to 100kHz spectrum. A frequency counter

connected to this signal then gives a count linearly proportional to the original analog voltage (VIN).

If a linearly-proportional analog output voltage is required, the counter can be replaced by a TC9400 used in the F/V mode.

HIGH NOISE IMMUNITY DATA TRANSMISSION

When transmitting analog data over long distances, it is advantageous to convert the analog signal into a digital signal, which is less

susceptible to noise pick-up.

In the system shown below, the TC9400 converts the input voltage into a pulse or square wave which is transmitted on a pair of wires

by use of a line driver and receiver. At the other end, the original voltage (VIN), can be digitally displayed on a frequency counter or

converted back to an analog voltage by use of a TC9400 F/V converter.

VIN

Digital Display

Gate

Latch Reset

Time Base

Counter

TC9400

V/F

Transmitter

Receiver

VIN

Analog Display

Digital Display

Gate

Latch Reset

Time Base

Counter

Twisted

Pair Cable

Differential

Driver

Differential

Line

Receiver

TC9400

V/F

9400

F/V

FIGURE 12: Telemetry.

FIGURE 13: High noise immunity data transmission.

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