Gas detector is usually used for multi-function combination, it is also a gas instrument sensor precision is relatively high equipment, traditional instrument calibration also needs to carry out multiple groups of experimental detection, and the calibration cycle is relatively short compared with general instruments and equipment, then what calibration specifications are gas detector instrument calibration?
First, Calibration of gas measurement systems project
1． Combustible gas Ex: alarm function and alarm action value inspection, indicating value error, response time, repeatability.
2． H2S: alarm function, display error, repeatability, response time.
3． O2: indicating error, repeatability, response time.
4． CO: alarm concentrated value, alarm function, indicating error, repeatability, response time.
In addition to the above main verification items, we should also check the most basic appearance and structure, signs and signs, etc., to ensure that each item is intact and clear and easy to identify. After the calibration of the gas detector, at least prepare the gas reference material, flow controller, zero gas, stopwatch, pressure reducing valve and gas circuit.
Second, the instrument calibration cycle
1． The accuracy of the gas detector mainly depends on the sensor, electrochemical sensor and catalytic combustion sensor in the process of use will be affected by some substances in the environment to change or even reduce its sensitivity, so regular calibration of the gas detector is completely necessary.
2． The usual instrument calibration cycle may be once a month, if the gas detector is not often used, there is no need for such maintenance. In this case, calibration can be carried out after each use, and it is recommended that the interval between the calibration date and the use date should not exceed 1 month.
In addition to instrument calibration, a functional test is recommended after each use to ensure the correct response of the instrument to the gas.
3． In order to detect the error of the instrument within the normal range, regular calibration is also necessary.
Calibration calibration method: First of all, zero gas and standard concentration gas calibration of the gas detector. The obtained standard curve is stored in the instrument. When measuring, the instrument compares the signal generated by the measured gas concentration with the signal of the standard concentration, and then calculates the accurate gas concentration.
Third, the instrument calibration and verification method.
1.Alarm function
Observe whether the sound, light or vibration alarm function of the instrument is normal, and record the alarm concentration value displayed by the instrument, that is, the alarm action value, through the gas standard material whose concentration is about 1.5 times the alarm setting value.
2.Repeatability
After the instrument is preheated and stable, adjust the instrument zero point with zero gas, and give the instrument a certain concentration range (such as: 40% of the full scale). Hydrogen sulfide: 50% of full scale. Oxygen: 80% full scale. CO: 70% upper limit of the measurement range), and record stable measurement data, repeat the operation 6 times, the relative standard deviation of one measurement is the repeatability of the instrument.
Gas detector in the long-term use of the process will produce drift, resulting in measurement errors and inaccurate measurement results, affecting the safety of the instrument, is the main reason why the gas detector needs to be checked regularly.
3.Wrong indication
Feed different concentrations of gas reference materials into the instrument and record the measurement results. The relative and absolute error of the instrument is calculated by the difference between the average value of the test result and the actual gas concentration.
4.Gas standard material concentration measurement in the value of the error is:
Ex: 10%, 40%, 60% of the whole series of gas reference substances.
H2S: 20%, 50%, 80% full range of gas reference materials.
O2:20%, 50%, 80% of the full scale gas reference material
CO: 1.5 times the instrument alarm (lower limit) set value, 30% of the upper limit of the measurement range and 70% of the upper limit of the measurement range.
Response time.
First, zero gas generator is introduced to calibrate the instrument. Second, the instrument is set to a certain concentration range (e.g., 40% of the total range). Hydrogen sulfide: 50% of full scale. Oxygen: 80% full scale. CO: 70% of the upper limit of the measurement range) gas standard material, stable after gas removal. Then the zero gas is reintroduced to stabilize the instrument. Finally, the gas reference material of the above concentration is introduced, and the stopwatch is used to record the time from the introduction to the instrument stable display of 90% concentration. The instrument response time was averaged three times.
As an instrument and equipment manager, we should be familiar with the calibration content of these instruments of the gas detector, scientifically plan the calibration cycle of the instrument, formulate a calibration plan, and ensure the normal use of the instrument and equipment.
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