SEL Multi-Channel Temperature Reader

Straight Engineering LLC (SEL) temperature instruments report temperature from multiple sensors. Different models have different numbers of channels and either support RTD or thermocouple sensors.

Ouput Format

Data for each channel is output as it is read by the instrument, at a fixed period of approximately 0.167 seconds. Data each channel except the final channel is terminated by “,”. Data for the final channel is terminated by \r\n.

Data for each channel is of the form: “Cnn=tttt.tttt” where:

  • nn is the zero-padded channel number.

  • Channel 00 is used to report the internal reference temperature for thermocouple sensor units. RTD sensors do not report a value for channel 00.

  • tttt.tttt is the temperature (C), in fixed floating-point format.

  • A specific temperature value is used to indicate an error; it depends on the sensor type:

    • RTD sensors: 9999.9990.

    • Thermocouple sensors: -201.0000.

    An error value typically means that the sensor is disconnected.

Example Output

Example output for 4-channel RTD instrument, with a 0.167 second pause between each channel:

C01=0032.1443,C02=0033.0320,C03=-001.3020,C04=-201.0000\r\n

Example output for a 4-channel thermocouple instrument, with a 0.167 second pauses between each channel. Note the extra channel 00 reading for the internal temperature reference:

C00=0025.4300,C01=0032.1443,C02=0033.0320,C03=-001.3020,C04=9999.9990\r\n

Serial Interface Parameters

  • RS-232

  • 19200 baud

  • 8 bits

  • no parity

  • 1 stop bit

  • no flow control

  • ASCII data format