Ambient Temperature Sensor - Novatech 1730 Series Reference Manual

Novatech Controls 1730 Series Diagnostics Mode Reference Manual
For testing the probe EMF input channels, the signal source must be capable of sending a DC voltage
signal in the range of -50mV to 2000mV.
NOTE: Signals outside of the range of -50mV to 2400mV may damage the analog input circuitry.
By modulating the output from the signal generator, the transmitter should be able to quickly and
accurately reflect the voltage or temperature changes on the second line of the display.
Failure to reflect these changes would indicate some fault between the input terminals and the channel
selection multiplexer components IC8/IC9. This may be caused by broken solder joints, damaged tracks
or ancillary components such as pull-up resistors.
Both of the temperature inputs have pull-up resistors that will cause the signal to read 1371.1°C if they
are open-circuit.

10. Ambient Temperature Sensor

Overview: The transmitter has a solid-state temperature sensor IC4 that is used to monitor case
temperature and for thermocouple cold-junction compensation. The sensor is located in the top-left
corner of the main PCB directly above the input terminals for probe #1, the analog output signal is sent
directly to the MCU.
Option Up/Down: no operation
Enter: no operation
The display should indicate ambient temperature in degrees Celsius. It should read close to room
temperature, possibly a couple of degrees higher due to heat dissipated from the transmitter circuitry.
To confirm the sensor is live reading temperature, try to warm it by touching it lightly with a finger, or
cooling it using air from a can.
The output from the temperature sensor can be read using a DMM as a DC signal via the unmarked test-
point directly adjacent to IC4. The component is a Texas Instruments LM50, which should output an
analog signal of 500mV offset plus 10mV/°C. For example at 25°C the signal should be (500mV +
25x10mV = 750mV)
The order for testing this sensor would be to confirm that the component IC4 is working using a DMM
on the unmarked adjacent test-point, then check whether the signal is being transmitted to MCU pin
P10_0.
11. Ambient RH Sensor
Overview: The transmitter has a solid-state relative humidity sensor IC30 that is used for oxygen
calculations. The sensor is located in the top-left corner of the main PCB above the analog input
circuitry. The analog signal is buffered via an op-amp IC31 and attenuated using two resistors, this
signal is sent directly to the MCU.
Option Up/Down: no operation
Enter: no operation
The display should show ambient air relative humidity as percentage. The reading will vary depending
on the ambient conditions.
The output from the humidity sensor can be read using a DMM as a DC signal via the unmarked test-
point directly adjacent to IC30. The component is a Honeywell HIH-4000-002, which outputs a linearised
voltage of ~825mV @ 0% RH through to ~3.75V @ 100% RH. The signal is sent to the MCU via op-amp
IC31 to buffer the signal and R127 & R128 that attenuate the signal by 50%.
Document Revision 1.03 Page 7 of 16 Diagnostics Mode v1.08