First, wiring: provide 24V DC power supply (voltage range 21-27V), measuring instrument or secondary display instrument, the power supply, measuring instrument or secondary display instrument according to the wiring requirements to connect the gas alarm.
Second, the warm-up: After the instrument is powered on, it should be warmed up in fresh air for a period of time, different gas alarm warm-up time requirements are different: most probes initial power-on warm-up time is less than 1 hour (ammonia, hydrogen chloride gas time should be 3 hours or longer). When the gas alarm is on for the first time, there will be a short-term signal output over-current condition, which is related to the nature of the electrochemical gas sensor. As the warm-up time is extended, the indication will gradually decrease to zero (do not artificially adjust the zero point). When the gas alarm indicator is reduced to zero, the gas alarm can enter the normal detection state. At this time, a small amount of gas can be detected (note that the concentration can not be too high, generally about 60% of the gas alarm range is appropriate. High gas concentrations can cause the sensor to poison or damage immediately.
Note: The gas and gas alarms have been strictly tested in accordance with the "National Measurement Verification Regulations of the People's Republic of China" at the time of shipment, and no calibration tests are required at the initial stage of installation.
Third, the gas alarm calibration:
Gas alarms should be calibrated after running for a period of time (typically 3-6 months). When verifying the calibration, relevant professionals should refer to “RB-TZ Oxygen and Toxic Gas Alarms†and verify or calibrate according to relevant national regulations.
Fourth, gas alarm zero calibration:
Configure high-purity nitrogen or fresh air, connect pipelines, pressure relief devices, standard ammeters and other related equipment. Connect the ammeter to the circuit board terminals of the gas alarm according to Figure 6. Connect the gas line to the calibration of the gas alarm. The connector and the flow meter, into the high-purity nitrogen or fresh air (Note: The flow rate should be controlled at 200-500ml/min or so), at this time, the gas alarm output should be "4mA", the circuit board sampling test point TP1 output voltage The value should be 40mV. Otherwise adjust the zero potentiometer (ie "O" potentiometer), note: turn the potentiometer clockwise, the output value decreases; counterclockwise potentiometer, the output value increases.
After the zero adjustment is completed, the range calibration can be performed as follows:
Through the calibration cap, introduce a standard gas equivalent to 60% of full-scale concentration (the gas concentration should not be greater than 80% of the instrument's range), wait until the instrument output value is stable to see if it corresponds to the standard gas concentration, otherwise adjust the calibration potentiometer (ie " S "potentiometer", so that the gas alarm in the case of a set range of the output value and standard gas concentration values ​​consistent. Note: Rotate the potentiometer clockwise to decrease the output value. Rotate the potentiometer counterclockwise to increase the output value.
Gas alarm output signal can be calculated by the following formula: Gas concentration Gas alarm output signal = 4+——————×16(mA)
The voltage signal at the measuring range circuit board TP1 should be:
Standard gas concentration V = 40+——————×160(mV)
For example, the measurement range is: (0-500)ppm gas detection probe, 50ppm
Standard gas concentration, sampling test point output value voltage:
50
V measurement=40+——————×160=56(mV)
500
The gas alarm signal output current is:
50
Detector output signal = 4+——————×16=5.6(mA)
500
After calibration, the standard gas is switched off and the gas detector is returned to zero in fresh air or nitrogen. If there is drift in the zero point, the zero point potentiometer can be readjusted, so that the gas alarm signal output is 4mA or the sampling test point output voltage is 40mV, and the standard gas equivalent to 60% of the span concentration is re-introduced. Repeat the above steps to make the gas alarm. The output voltage of the instrument signal output or sampling test point corresponds to the standard gas concentration value.
Note when venting: The standard gas flow rate can be 200~500ml/min but the flow must be kept constant.
Note: The "B" and "4" potentiometers on the circuit board are used to adjust the potentiometer for the gas alarm circuit. Users should not adjust it by themselves. Otherwise, it will have a crucial influence on the detection of the instrument.
Gas gas alarm Do not disassemble the sensor shield or wipe the sensor surface by hand during calibration to prevent contamination of the sensor.
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