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Shanghai Automation Instrumentation Co., Ltd.
Address:No.191 Guangzhong Road (West) Shanghai
Tel:86-21-59189606
Fax:86-21-60917975
Website:www.sc-saic.com/english
E-mail: tom.saic@gmail.com

Pressure transmitter calibration method
Release time:2016-12-13   Clicks:783


A measuring instrument for pressure transmitters is an important measure, and in many areas there are bound to use sideways. Pressure transmitter at the time the application is need to check through the line, the pressure transmitter calibration time also need to have an accurate way. So what detailed validation approach is it? Tomorrow for the big home Xiaobian first volume pressure transmitter accurate calibration approach it.
Preparatory Task
Differential pressure transmitter is in use in the guide tube dovetail pressure, normally the practice, need to guide the pressure tube with differential pressure transmitter open discussion, then access gauge stop calibration. Such as Xu is very troublesome, and the task now rest intensity large, most worried about is dismantling discussion pull off the pilot pressure pipe leak or rendering performance. We know no matter what type of differential pressure transmitter, its positive and negative pressure chamber has a vent, drain valves or cocks; this is our on-site calibration of differential pressure transmitter provides a convenient, that does not have to remove lead pressure pipe can be calibrated differential pressure transmitter. Differential pressure transmitter stops the timing of school, the first positive and negative valve closed three valves, and open the balanced valve, then unscrew the vent and drain valves or cocks vent, and then use the discussion to replace the pick positive pressure self-denial chamber exhaust gap gauge drain valve or cock; and a negative pressure chamber insisted loosen condition to pass big air. Pressure source through the hoses and Katsumi discuss convergence, equalization valve closed, and review the gas path seal the case, then the ammeter (voltmeter), handheld access to the transmitter output circuit, beginning calibration after power to warm up.
Differential pressure transmitter calibration routine
First damping to zero situation, to emphasize zero, then add full scale pressure span adjustment, so that the output of 20mA, the adjustment at the scene talking about the fast, in this first volume of zero and span of rapid adjustment method. Almost zero when the number of transfer does not affect the full-scale, full-scale but adjusted for zero impact, without migration when its influence range of about 1/5 of the amount of toner that span adjust upwards 1mA, Zero will move up about 0.2 mA, and vice versa. For example: Enter the full scale pressure 100Kpa, the reading of 19.900mA, tune span potentiometer allows output 19.900+ (20.000-19.900) * 1.25 = 20.025mA range growth 0.125mA, the zero growth of 1/5 * 0.125 = 0.025. . zero adjustment potentiometer allows output 20.000mA. Zero span calibration with the later often, and then review each of the scale side, to see whether the ultra-poor? Need to stop trimming. Then stop migration, linear, damping swap tasks.
Smart Pressure Transmitter Calibration
The practice of using the approach described above are not smart transmitter calibration stop, since it is constructed by the HART transmitter the truth of the resolution. Since the smart transmitter between 4-20mA current signal source with the input pressure occurs, in addition to machines, circuits, and another microprocessor chip input data computing tasks. Thus adjustment measures and practices vary.
Some people think that only with the HART Communicator can change the smart transmitter degree range, and can be stopped with the zero adjust span task, without the need to input pressure source, but this practice can not be called calibration, only called the set range. The real is the need to calibrate the scale using a pressure source input of the transmitter. Because they do not apply the scale and tone control range (LRV, URV) is not calibrated, negligence input department (pressure transmitter input) to stop output conditioning (transmitter conversion circuit) is not an accurate calibration. Further pressure, differential pressure detecting means and the A / D converter circuit, the current output and the associated error or the like, the calibration target is to identify changes associated with the three. Exaggerate the point: Only input with output (pressure transmitter input, A / D converter circuit, the loop current output circuit) together debugging can be called a true sense of the calibration.
 
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