JPH0371653B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for diagnosing performance deterioration of a diaphragm occurring in a pressure transmitter such as a differential pressure transmitter.

[Conventional technology]

A pressure transmitter that measures pressure, differential pressure, etc. is equipped with a high pressure chamber and a low pressure chamber via a center diaphragm, each chamber is sealed with a diaphragm such as a barrier diaphragm, and a sealed liquid such as silicone liquid is introduced into each chamber. The barrier diaphragm that isolates each chamber from the outside is manufactured as a highly durable product.
Depending on the usage conditions, corrosion may occur due to the adhesion of the fluid in contact or the action of the fluid in contact, which changes the mechanical properties and makes it difficult to accurately transmit the pressure to be measured to each chamber. In this case, the detection output of the pressure transmitter becomes inaccurate, so conventionally, the presence or absence of an abnormality was determined empirically according to the value of the detection output, or the pressure transmitter was checked through periodic inspection. is checked to diagnose the presence or absence of abnormalities due to performance deterioration of the barrier diaphragm.

[Problem that the invention seeks to solve]

However, judgment based on experience can only yield inaccurate results, and periodic inspections require various measuring instruments and a lot of effort. This is creating a problem that makes it necessary.

[Means for solving problems]

In order to solve the above-mentioned problem, the present invention is constructed by the following means.

That is, the initial constants required to calculate the compliance of the diaphragm of a pressure transmitter equipped with a high-pressure chamber and a low-pressure chamber that are isolated from the outside by each diaphragm and filled with a sealed liquid are stored in a memory, and each of the above-mentioned A static pressure sensor that detects at least one static pressure in the room and a temperature sensor that detects the temperature of the pressure transmitter are provided, a known pressure is applied to the pressure transmitter, and the detected output of the pressure transmitter and the static pressure at this time are The compliance of at least one of the diaphragms is calculated using each detection output of the sensor and the temperature sensor and the initial constant of the memory, and the performance of the diaphragm is diagnosed according to the compliance value.

[Effect]

Therefore, if the compliance of the diaphragm deviates from the predetermined range or changes from the initial value,
It is possible to diagnose that the performance of this has deteriorated.

〔Example〕

Hereinafter, details of the present invention will be explained with reference to figures showing examples.

FIG. 2 is a sectional view of the differential pressure transmitter, in which covers 2a and 2b having through holes 1a and 1b to which the pressure to be measured is applied are connected to gaskets 3a and 3b from both sides.
The bodies 4a and 4b are sealed in a sealed manner.
, barrier diaphragms 5a, 5b are provided in close contact with the bodies 4a, 4b around the periphery, facing the through holes 1a, 1b, and gaps 6a, 6 are provided inside each of the barrier diaphragms 5a, 5b.
b are formed, and these central parts and communication holes 7a, 7
A center diaphragm 9 is provided between the inner chambers 8a and 8b, which communicate with each other through b, for sealingly separating the inner chambers 8a and 8b.

Further, there is a gap 6 below the bodies 4a, 4b.
communicates with a, 6b and inner chambers 8a, 8b, and
Communication holes 12a, 12b are provided which communicate with the injection ports 11a, 11b for the filled liquids 10a, 10b, and inner chambers 8a, 8 are provided above the bodies 4a, 4b.
The covers 2a, 2b and the bodies 4a, 4b are tightly secured to each other by bolts 14 and nuts 15, respectively.

On the other hand, an annular gap 2 is provided between the outer cylinder 21 fixed to the upper surface of the bodies 4a and 4b by welding.
A cylindrical member 23 is provided which forms a cylindrical member 2 and is fixed in the same manner.
A support cylinder 25 made of glass is fixed to the lower surface of the sensor base 24 that fits into the interior of the sensor base 24 in close contact with the periphery of the upper end, and the sensor base 24 and the support cylinder 25
A communication hole 26 connecting the gap 22 and the lower surface of the support tube 25 is bored in the support tube 2.
A diaphragm-shaped composite sensor 27 is fixed to the lower surface of the sensor 5 to seal the communication hole 26 from the surroundings.

Further, a sleeve 28 is fixed to the lower surface of the sensor base 24, forming a gap with the support cylinder 25 and the cylindrical member 23, and protruding below the composite sensor 27. A shield plate 29 for noise prevention having a through hole is attached.

Note that the lead wire of the composite sensor 27 passes through the sleeve 28 and the sensor base 24, is led out to the pins 20a and 20b on the top surface, and is connected to a circuit in the pressure transmitter 30 that is locked upward.

FIG. 1 is an enlarged plan view of the composite sensor 27, in which a substrate 31 made of silicon or the like is used, and a diaphragm 32 is formed in the center of the substrate 31.
Differential pressure sensors 33a to 33d are formed near the boundary between the diaphragm 32 and the substrate 31 on four diagonal sides using integrated circuit technology on these insulating film surfaces, and static pressure sensors are formed near these and on the substrate 31. 34a to 34d are formed, while a temperature sensor 35 is formed on the substrate 31 approximately in the middle between the differential pressure sensors 33a and 33b.
For the temperature sensor 35, a semiconductor element that functions as a strain gauge is used, and as the temperature sensor 35, a semiconductor element that functions as a thermistor is used.

Further, the differential pressure sensors 33a to 33d and the static pressure sensors 34a to 34d are connected in a bridge shape by a conductor 36, and each connection point is connected to a lead wire by a land 37, so that the strain on the diaphragm 32 is reduced. The differential pressure between the two surfaces of the diaphragm 32 is detected by the resistance value change of the differential pressure sensors 33a to 33d in response to the change in the resistance value of the substrate 31 and the static pressure sensor 34a in response to the static pressure applied to the surfaces on which the static pressure sensors 34a to 34d are formed. Since the resistance values of the static pressure sensors 34a to 34d change due to the difference in compression ratio between the static pressure sensors 34a to 34d, the static pressure is detected based on this.

Note that the temperature sensor 35 has a resistance value that changes depending on the ambient temperature, which causes the differential pressure sensor 33a to
It is designed to detect the temperature of the entire differential pressure transmitter including 33d to 33d.

Therefore, if high pressure P _H is applied to the through hole 1a side in FIG. 2 and low pressure P _L is applied to the through hole 1b side, the barrier diaphragms 5a, 5
b is displaced, this displacement is applied to the center diaphragm 9 via the filled liquids 10a and 10b, and P _H and
According to the differential pressure with P _L , the center diaphragm 9
is displaced, thereby absorbing most of the differential pressure, while a portion of the differential pressure is applied to the diaphragm 32 of the composite sensor 27 via the communication holes 13a, 13b, the gap 22, and the communication hole 26, and this The differential pressure between P _H and P _L is detected by the differential pressure sensors 33a to 33d according to the strain _of
Or the static pressure of P _L is detected, and these detection conditions are shown by the broken line in Figure 2 of the pressure transmitter 3.
0 as an electrical signal.

FIG. 3 is a schematic diagram showing the differential pressure transmitter described above, and in order to explain the principle of diagnosing the leakage situation of the sealed liquids 10a and 10b, the signals are determined as follows.

V _H : Total volume of the high pressure chamber 41 including the inner chamber 8a and parts communicating with it V _L : Total volume of the high pressure chamber 42 including the inner chamber 8b and parts communicating with it P _H : Applied high pressure P _L : Applied low pressure P _h : Static pressure in the high pressure chamber 41 P _l : Static pressure in the low pressure chamber 42 ΔV _H : Amount of displacement of the barrier diaphragm 5a ΔV _C : Amount of displacement of the center diaphragm 9 ΔV _L : Amount of displacement of the barrier diaphragm 5b Φ _H : Compliance of barrier diaphragm 5a Ф _C : Compliance of center diaphragm 9 Φ _L : Compliance of barrier diaphragm 5b Δ _V0 : Amount of change in volume of high pressure chamber 41 Δ _V2 : Amount of change in volume of low pressure chamber 42 α: Temperature of sealed liquids 10a, 10b Expansion coefficient ΔT: Temperature difference from the initial temperature at the time of shipment from the factory Furthermore, using the above-mentioned symbols, the following formula generally holds true in the configuration shown in FIG. 3.

P _H −P _h =1/Φ _H ΔV _H …(1) P _l −P _L =1/Φ _L ΔV _L …(2) P _h −P _l =1/Φ _C ΔV _C …(3 ) Δ _V1 = ΔV _C −ΔV _H +α・V _H・ΔT ……(4) Δ _V2 = ΔV _L −ΔV _C +α・V _L・ΔT ……(5) Here, the pressure transmitter 30 is V _H , based on the design value or measured value, to the memory of
V _L , Φ _C , α, and the actual measured temperature T ₀ at this time are each stored as initial constants, and the pressures P _H and P _L applied to the differential pressure transmitter are adjusted by opening and closing the pipes leading thereto. For example, P _H =10Kgf/cm ² , P _L =0, Kg
Assuming a known pressure of f/cm ³ , the detection output (P _h −P _l ) as a differential pressure oscillator obtained by the differential pressure sensors 33a to 33d at this time and the static pressure sensors 34a to
By determining the detection output P _h or P _l from the temperature sensor 34b and the detection output T from the temperature sensor 35, the respective compliances Φ _H and Φ _L of the barrier diaphragms 5 a and 5 b can be calculated based on the above equation.

That is, the following equation is obtained from equation (3).

ΔV _C = Φ _C (P _h −P _l ) ...(6) Also, in equations (4) and (5), the filled liquids 10a and 10b
If there is no leakage and Δ _V1 = 0 and Δ _V2 = 0, the following equation can be obtained.

ΔV _H = ΔV _C +α・V _H・ΔT ……(7) ΔV _L = ΔV _C +α・V _L・ΔT ……(8) If either P _h or P _l is found,
The detection output (P _h − P _l ) of the differential pressure transmitter is known,
When (P _h −P _l )=K, the other can be obtained by P _h =K+P _l P _l =P _h −K (9).

Therefore, from equations (1), (2) and equations (6) to (9), the respective compliances Φ _H and Φ _L of the barrier diaphragms 5a and 5b are given by the following equations.

Φ _H = Φ _C (P _h − P _l ) + α・V _H・ΔT/(P _H −P _h )……(
10) Φ _L = Φ _C (P _h − P _l ) + α・V _L・ΔT/(P _l − P _L )……
(11) However, ΔT=T−T ₀ Therefore, each initial setting V _H , V _L ,
In addition to reading and using Φ _C , α, and T ₀ , the detection output of each sensor (P _h −P _l ), P _h or P _l , and
By calculation using T, Φ _H and Φ _L can be calculated.

These Φ _H and Φ _L are the current barrier diaphragm 5
This is the compliance that a and 5b have, and the upper and lower limits determined in advance according to the measurement tolerance are compared with the values obtained by equations (10) and (11), or the initial values are stored in memory. By storing each compliance and performing a similar comparison, it is possible to reliably diagnose the presence or absence of performance deterioration of the barrier diaphragms 5a and 5b.

FIG. 4 is a block diagram of an example of a circuit configuration based on the above principle, and shows the differential pressure transmitter (hereinafter referred to as
DPT) 51 and a pressure transmitter (hereinafter referred to as
PTR) 30, the differential pressure sensor (hereinafter referred to as DPS) 33 and the static pressure sensor (hereinafter referred to as SPS) in Fig. 1 are used.
34, and a detection circuit (hereinafter referred to as TS) that detects each resistance value change of temperature sensor (hereinafter referred to as TS) 35 (hereinafter referred to as DET).
Each detection output from 52 is sequentially and repeatedly selected by a multiplexer (hereinafter referred to as MPX) 53, and then converted into an analog-to-digital converter (hereinafter referred to as ADC).
54 converts the signal into a digital signal and supplies it to a processor (hereinafter referred to as CPU) 55 such as a microprocessor, which normally converts the detection output of DPS 33 into a differential pressure measurement value by a predetermined calculation and converts it into a digital signal (hereinafter referred to as CPU). , DAC) 56 and a drive circuit (hereinafter referred to as DR) 57, it is applied as a forward bias corresponding to the measured value to transistor (hereinafter referred to as TR) Q ₁ to control the collector-emitter resistance value of TR Q ₁ . Based on the power supply E applied to the two-wire transmission line consisting of the lines L ₁ and L ₂ via the resistor R, a current with a unified signal of, for example, 4 to 20 mA is passed, and the measured value is transmitted based on the current value. This current value is detected as the terminal voltage of the resistor R, and this is given to the control device etc. as a measurement signal S _n .

Further, the voltage change between the lines L ₁ and L ₂ is detected by a comparator (hereinafter referred to as CP) 58 after comparing it with the reference voltage E _S1 , and is given to the CPU 55 via the ADC 59', and this is sent to the CPU 55 as a received signal. is to be deciphered and to respond to the contents.

Note that the CPU 55 has fixed memory (hereinafter referred to as
It executes the instructions in the non-volatile memory (hereinafter referred to as NVM) 61 while accessing the necessary data to variable memory (hereinafter referred to as RAM) 60.
Each of the above-mentioned initial constants is stored in the initial constants at the time of shipment from the factory.

On the other hand, the portable tester (hereinafter referred to as PST) 70 is bridge-connected to the lines L ₁ and L ₂ by lead wires l ₁ and l ₂ .
It is possible to freely transmit and receive signals based on voltage changes between lines L ₁ and L ₂ , and keyboard (hereinafter referred to as KB) 7
The CPU 72, which is similar to the CPU 55, responds to the operation of 1, and transmits TR/TR via the DAC 73 and DR 74.
By controlling Q ₂ and passing a current other than the current flowing through TR/Q ₁ from the power source E as a coded pulse, the line voltage is changed in a pulse, and the transmission to PTR 30 is changed. At the same time, the line voltage corresponding to the current value change controlled by TR Q ₁ is detected by comparison with the reference voltage E _S2 in the CP75, decoded by the CPU 72 via the ADC 76, and displayed by the display (hereinafter referred to as DP) 77. It is designed to display information.

Note that the CPU 72 also performs calculations and control by executing instructions in the ROM 78 and accessing necessary data from the RAM 79.

Therefore, the PST 70 can check the measured values of the PTR 30, as well as send various commands to the PTR 30 and receive response transmissions in response to these commands. If you do this, this will be received by the CPU 55 of the PTR 30,
In response to this, the CPU 55 transmits each initial constant in the NVM 61 by the current change of the pulse code, and sequentially takes in each detection output of the DPS 33, SPS 34, and TS 35 via the DET 52 and MPX 53, and calculates each detection value based on these. Since these are transmitted in the same way, these are received by the CPU 72, and the CPU 72 uses them to perform the above (10).
The calculation according to equation (11) is executed, and the above-mentioned judgment is made according to the result, and the diagnostic status based on this is displayed on the DP 77.

Figure 5 shows the external shape of PTS70, A is a front view,
B is a side view, in which all the circuits and power supply are housed in a handheld outer casing 81, and a plurality of pushbutton keys 8 are shown on the front.
A KB71 consisting of 2 parts is provided, and a DP77 such as a liquid crystal display element is attached above this, and lead wires connected to tip helicips 83a and 83b are provided.
A code 84 consisting of l ₁ and l ₂ is derived, and from this,
The lines L ₁ and L ₂ can be freely connected to terminal boards, etc.

Therefore, if you make the above connection using the clips 83a and 83b and then press the "DIA CHECK" key 82, the above judgment will be made through transmission/reception and calculation by the internal CPU 72, and the DP
77, for example "HP DIA ABNORMAL"
is displayed, which immediately indicates the performance deterioration of the barrier diaphragm 5a of the high pressure chamber 42. Therefore, this diagnosis of abnormality in the barrier diaphragm 5a of the DPT 51 can be easily and accurately performed without preparing any special measuring equipment. It is done.

However, in addition to using the barrier diaphragms 5a and 5b, the same applies when using various diaphragms with equivalent functions, and it can be applied not only to the measurement of differential pressure but also to the measurement of absolute pressure. Depending on the situation, only one of equations (10) and (11) may be calculated, and the diagnosis may be made only for the diaphragm that is in contact with the fluid that affects the performance of the diaphragm. It is also possible to store only the initial value corresponding to the value in the memory.

In addition, the NVM 61 may be one that is attached to the DPT 51, and it is also possible to use other memory elements that can retain the contents for a long time, and the above-mentioned calculations and judgments are performed in the CPU 55 of the PTR 30.
Alternatively, it may be performed by a CPU such as a control device, and the diagnosis results may be displayed on a separate display.
In addition to what is shown in the figure, you can select according to the conditions, etc.
Various modifications are possible.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, it is possible to easily and accurately diagnose performance deterioration occurring in the diaphragm of differential pressure transmitters, etc. Remarkable effects can be obtained.

[Brief explanation of drawings]

The figures show embodiments of the present invention, in which Figure 1 is a plan view of a composite sensor, Figure 2 is a sectional view of a differential pressure transmitter, and Figure 3 is a cross-sectional view of a differential pressure transmitter.
The figure is a schematic diagram of the differential pressure transmitter, FIG. 4 is a block diagram of the circuit configuration, and FIG. 5 is an outline diagram of the portable tester. 5a, 5b... Barrier diaphragm, 7a, 7
b, 13a, 13b, 26...Communication hole, 8a, 8
b...Inner chamber, 9...Center diaphragm, 10
a, 10b...Filled liquid, 27...Composite sensor, 3
0... Pressure transmitter, 31... Board, 32... Diaphragm, 33, 33a to 33d... DPS (differential pressure sensor), 34, 34a to 34d... SPS (static pressure sensor), 35... TS ( temperature sensor), 41...high pressure chamber, 42...low pressure chamber, 51...DPT (differential pressure transmitter), 55, 72...CPU (processor), 59,
78...ROM (fixed memory), 60, 79...
RAM (variable memory), 61...NVM (non-volatile memory), 58, 75...CP (comparator), 71...
KB (keyboard), 77...DP (display), Q ₁ ,
Q ₂ ...TR (transistor), L ₁ , L ₂ ... line,
l ₁ , l ₂ ... Lead wire, E ... Power supply.

Claims (1)

[Claims] 1. Store in memory the initial constants required to calculate the compliance of the diaphragms of a pressure transmitter equipped with a high pressure chamber and a low pressure chamber that are isolated from the outside by each diaphragm and filled with a sealed liquid, and A static pressure sensor that detects at least one static pressure in the room and a temperature sensor that detects the temperature of the pressure transmitter are provided, a known pressure is applied to the pressure transmitter, and the detection output of the pressure transmitter at this time is and calculating the compliance of at least one of the diaphragms using each detection output of the static pressure sensor and the temperature sensor and the initial constant of the memory, and performing a performance diagnosis of the diaphragm according to the compliance value. A method for diagnosing the performance of a diaphragm in a pressure transmitter.