JPS6361929A - Diaphragm performance diagnosis method for pressure transmitters - Google Patents

Abstract

PURPOSE:To easily and accurate diagnose the performance deterioration of the diaphragm of a differential pressure transmitter, etc., by calculating the compliance of at least one diaphragm. CONSTITUTION:Respective resistance value variations of a differential pressure sensor (DPS) 33, a static pressure sensor 34, and a temperature sensor 35 are detected 52 and the detection output is converted into a digital signal through a multiplexer 53 and an analog-digital converter 54 and then supplied to a CPU55. Here, the detection output of the DPS33 is normally converted into a differential pressure measured value and the collector-emitter resistance values of the digital-analog converter 56 and driving circuit Q1 are controlled to send out the measured value with a current value on the basis of a power source E applied to a two-wire transmission line through a resistor R. Then the current value is detected as the terminal voltage across the resistance R and supplied as a measurement signal Sm to a controller, etc. Consequently, the performance deterioration of the diaphragm of the differential pressure transmitter, etc., is easily and accurately diagnosed.

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 used to measure 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 silicone liquid etc. is injected into each chamber. The barrier diaphragm that seals the filled liquid and isolates each chamber from the outside is manufactured as a highly durable product, but depending on the usage conditions, it may be susceptible to adhesion of the fluid it comes in contact with.
Alternatively, corrosion may occur due to the action of the fluid in contact, which changes the mechanical properties and makes it impossible to accurately transmit the pressure to be measured into each room. Conventionally, the detection output of the barrier diaphragm is inaccurate, so in the past, the presence or absence of an abnormality was determined empirically based on the detection output value, or the pressure transmitter was checked through periodic inspections, and the pressure transmitter was checked based on the performance deterioration of the barrier diaphragm. Diagnosing the presence or absence of an abnormality.

[Problem that the invention seeks to solve]

However, judgment based on experience can only yield inaccurate results, and periodic inspection requires a separate measuring device and a lot of effort. This is creating a problem that requires additional support.

[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 The compliance of at least one of the diaphragms is calculated using each detection output of the pressure sensor and the temperature sensor and the initial constant of the memory, and the performance of the diaphragm is diagnosed according to this compliance value.

[Effect]

Therefore, if the compliance of the diaphragm deviates from a predetermined range or changes from its initial value, it can be diagnosed that the performance of the diaphragm has deteriorated.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to figures showing examples.

Figure 2 is a cross-sectional view of the differential pressure transmitter, with through holes 1a and 1b through which the pressure to be measured is applied, and covers 2m and 2b with through holes 1a and 1b.
Barrier diaphragms 5a, 5b surround the bodies 4a, 4b, which are hermetically sealed with gaskets 3a, 3b from both sides, facing the through holes 1m, 1b.
It is installed in close contact with M and 4B.

Gaps 5m and 9b are formed inside each of these, and inner chambers 8m and 8b communicate with the center of these through communication holes 7m and 7b.
A center diaphragm 9 is provided between each of the inner chambers 9 m and 9 to airtightly isolate the space between the inner chambers.

Further, below the bodies 4h and 4b, a sealed liquid 10a is communicated with the gaps sa and sb and the inner chambers 13m and 8b.

Communication hole 1 communicating with injection ports 11a and 11b of 10b
2a.

12b is provided, and above the bodies 4*, 4b are communication holes 13m, 13b between the inner chamber gm, 8b and the upper surface side.
are drilled, covers 2a, 2b and body 4m,
4b is tightly secured to bolt 14 and nut 15.

On the other hand, on the upper surface of the bodies 4m and 4b, a cylindrical member 23 is provided in an outer cylinder 21 fixed by welding and similarly fixed with an annular gap 22 therebetween.
A support made of glass is attached to the lower surface of the sensor space 24, which is in close contact with the upper end of the cylindrical member 23 to seal the open upper end of the outer cylinder 21, and which is in close contact with the upper end of the cylindrical member 23 and is fitted into the interior thereof. The tube 25 is fixed 9, and the sensor base 24 and the support tube 25 are provided with a communication hole 26 that communicates between the gap 22 and the lower surface of the support tube 25, and also communicates with the lower surface of the support tube 25. A diaphragm-shaped composite sensor 2γ is fixed to seal the 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.

Incidentally, the lead wire of the composite sensor 27 passes through the sleeve 28 and the sensor space 24, and connects to the bins 20m and 2 on the top surface.
0b and is connected to the circuit in the pressure transmitter 30 locked upward.

FIG. 1 is an enlarged plan view of the composite sensor 27.

An O substrate 31 such as silicon is used, and a diaphragm 32 is formed in the center thereof, and the diaphragm 32 and the substrate 3 are formed on the surface of these insulating films by integrated circuit technology.
Differential pressure sensors 3 are installed near the boundary with 1 and on diagonal lines from each other.
3a to 33d are formed, and static pressure sensors 34a to 34d are formed near these sensors and on the substrate 31, while a temperature sensor 35 is formed on the substrate 31 approximately midway between the differential pressure sensors 33m and 33b. Oshi, differential pressure sensor 33&~
33d and the static pressure sensors 34a to 34d, semiconductor elements that function as strain gauges are used, and as the temperature sensor 35, semiconductor elements that function as a thermistor are used.

Additionally, differential pressure sensors 33a to 33d and static pressure sensors 34a to
34d is connected in a bridge shape by a conductor 36, and each connection point is connected to a series lead wire by a land 3T, and the resistance value of the differential pressure sensors 33a to 33d corresponds to the distortion of the diaphragm 32. Due to changes, diaphragm 32
The static pressure sensors 34a to 34 detect the differential pressure between both sides.
Due to the compressibility difference between the substrate 31 and the static pressure sensors 34a to 34d, which corresponds to the static pressure applied to the forming surface of d, the static pressure sensor 3
Since the resistance values of 4a to 34d change, the static pressure is detected based on this.

Note that the resistance value of the temperature sensor 35 changes depending on the ambient temperature, and this causes the temperature sensor 35 to function as a differential pressure sensor. The temperature of the entire differential pressure transmitter including 33a to 33d is detected.

Therefore, if high pressure PM is applied to the through hole 1a side in FIG. 2 and low pressure PL is applied to the through hole 1b side, the barrier diaphragms 5a and 5b will be displaced accordingly, and this displacement will cause the filled liquid to 10m, 10b to the center diaphragm S, and the center diaphragm 9 is displaced according to the differential pressure between Pg and Pt, thereby absorbing most of the differential pressure "C". ,
Gap 22. A part of the differential pressure passes through the communication hole 26 to the composite sensor 2.
The differential pressure between PH and Pt is applied to the diaphragm 32 of No. 7, and the differential pressure between PH and Pt is detected by the differential pressure sensors 33a to 33d according to the strain thereof. 34d detects the static pressure of P or PL, and the detection status is sent out as an electrical signal via the pressure transmitter 30 shown by the broken line in FIG.

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 liquid 10m, 10b, the following symbols are defined.

Total volume of the high pressure chamber 41 including the VMa internal chamber 8a and parts communicating with it L: Total volume of the low pressure chamber 42 including the internal chamber 8b and parts communicating with it P+i: Applied high pressure PLe Applied low pressure Ph: High pressure chamber 41 Static pressure Pt inside: Static pressure Δ■ inside the low pressure chamber 42! I: Displacement amount Δvc of the harrier diaphragm 5a: Displacement amount ΔvL of the center diaphragm 2m 9: Displacement amount Φ3 of the harrier diaphragm 5b: Compliance ΦC of the barrier diaphragm 5a: Compliance ΦL of the center diaphragm 9: Compliance Δ7 of the barrier diaphragm 5b! : Volume change amount Δ7□ of high pressure chamber 41 : Volume change amount α of low pressure chamber 42 : Temperature expansion coefficient ΔT of enclosed gloa, 1ab:
Temperature difference from the initial temperature at the time of factory shipment Also, using the above-mentioned symbols, the following formula generally holds true in the configuration of FIG. 3.

1...(1) PtI Ph=Stone ΔV・PA Pt,=Soil ΔvL---(2) ΦL Δ72 = l'1. jVc+α'V,,"j'
f * * m (5) Here, (V,) is stored in the memory in the pressure transmitter 30 at the time of factory shipment based on the design value or the actual measurement value.

vL, Φ. , α, and the actually measured temperature T at this time.

are respectively stored as initial constants, and the pressures Pg, P1 . For example, P tx =L OK5' f /Crn2 by opening and closing the pipes leading thereto.
r P L = OKS' f A known pressure of 7 cm2 is assumed, and the detection output (Ph Pz) as a differential pressure transmitter obtained by the differential pressure sensors 33a to 33d at this time and the detection by the static pressure sensors 34a to 34d By determining the output Ph or Pt and the detection output T from the temperature sensor 35, each compliance Φ, Φ, of the barrier diaphragm 5at5b can be calculated based on the above equation.

In other words, a υ-order equation is obtained as shown in equation (3).

Δvc=Φc (Ph-Pz=) -----
-(6) Also, in equations (4) and (5), the filled liquid 1
There is no leakage of Qa, 10b, and Δma1=0. Δ7. =
If O, then linear formula % formula % In addition, if either Ph or Pt is found, the detection output of the differential pressure transmitter (Ph - P17 is known, υ, (Ph
-Pt)=, the other can be obtained by k'1-=Ph-.

Therefore, equations (1), (2) and (6) to (9)
), the respective compliances Φyo and Φ of the barrier diaphragms 5m and 5b are given by the following formulas.

Therefore, each initial constant VNIVLIΦC1 in memory
Φ, , Φ can be calculated by reading out and using α+'r6- and performing calculations using the detection output (ph-pt) of each sensor, ph or Pt, and T.

Φ1. Φ is the current barrier diaphragm 5m, 5
The compliance of b is the upper and lower limits determined in advance according to the measurement tolerance, and αG, (
111) or store each compliance of the initial case in memory.
If a similar comparison is made, the barrier diaphragm 5a
, 5b can be reliably diagnosed as to whether or not the performance has deteriorated.

FIG. 4 is a block diagram of an example of a circuit configuration based on the above principle.
In the pressure transmitter (hereinafter referred to as PTR) 30 connected to the differential pressure sensor (hereinafter referred to as DPS) 33 in FIG. Static pressure sensor (hereinafter referred to as 5PS) 34. and.

Each detection output from a detection circuit (hereinafter referred to as DET) 52 that detects each resistance value change of a temperature sensor (hereinafter referred to as TS) 35 is
A multiplexer (hereinafter referred to as MPX) 53 sequentially and iteratively selects the signal, converts it into a digital signal through an analog-to-digital converter (hereinafter referred to as ADC) 54, and then outputs the signal to a processor such as a microprocessor (hereinafter referred to as CPU) 55.
Here, the detection output of the DPS 33 is normally converted into a differential pressure measurement value by a predetermined calculation, and then digitally converted.
A transistor (hereinafter referred to as TR) is connected via an analog converter (hereinafter referred to as DAC) 56 and a drive circuit (hereinafter referred to as DR) 57.
) to Ql as a forward bias corresponding to the measured value,
The collector-emitter resistance value of TR/Ql is controlled, and based on the power supply E applied via the resistor R to the two-wire transmission line consisting of lines L1 r L2, for example, 4 to 20 m.
The measured value is transmitted through the current based on the unified signal of A, and the current value is
It is detected as the terminal voltage of resistor R, and this is the measurement signal S.
It is given to the control device etc. as m.

Further, the voltage change between the lines Ll r L2 is determined by the reference voltage E3. The received signal is detected by comparison with the received signal, and is sent to the CPU 55 via the ADC 59''.The CPU 55 decodes this as a received signal and responds to the contents thereof.

Note that the CPU 55 has a fixed memory (hereinafter referred to as ROM) 59.
It is assumed that the non-volatile memory (hereinafter referred to as NVM) 61 performs predetermined calculations and control while executing the instructions in it and accessing the necessary data to variable memory (hereinafter referred to as RAM) 60. , the above-mentioned initial constants are stored at the time of factory shipment.

On the other hand, the lead wire tl*62 connects the line L1e L
A portable tester (hereinafter referred to as PTS) 70 connected to 2 via a bridge is capable of freely transmitting and receiving signals based on voltage changes between the lines Ll * L2, and can transmit and receive signals based on voltage changes between lines Ll and L2, depending on the operation of a keyboard (hereinafter referred to as KB) 71. CPU72 similar to CPU55 responds,
By controlling TR"Q2 via the DAC73 and DR74, passing a current other than the current flowing through TR"QI from the power source E, and performing this in a coded pulse form, the line voltage is changed in a pulse form. At the same time, the line voltage corresponding to the current value change controlled by TRQ+ is set to the reference voltage E in the CF25.
It is detected by comparison with s2, and CP is detected via ADC76.
It is decoded by U72 and displayed by display device (hereinafter referred to as DP) 77.

Note that the CPU 72 also executes the instructions in R2M17 and
Computation and control are performed by accessing necessary data to AM79.

Therefore, the PTS 70 can check the measured value of the PTR 30, send various commands to the PTR 30, and receive corresponding response transmissions, and the KB 71 can send commands to check the barrier diaphragm. If you do this, this will be the CPU5 of PTR30.
5, and in response, the CPU 55
In addition to transmitting each initial constant in 1 according to the current change of the pulse code, each detection output of DPS33.5PS34 and TS35 is transmitted to 11 through DET52 and MPX53.
Next, since each detected value based on these is transmitted in the same way, these are received by the CPU 72, and using these, the CPU 72 executes the calculations based on the above-mentioned σ■, (ID formula, and 1. The above-mentioned judgment is made according to this result, and the diagnostic status based on this is displayed on the DP 77.

Figure 5 shows the external appearance of PTS70, the figure is a front view, and (B)
is a side view), all the circuits and power supply are housed in the outside of the handheld type 81, and the KB consisting of a plurality of push button keys 82 is located on the front.
71 is provided, and a D of a liquid crystal display element, etc. is provided above this.
Attach P77 and clip to the tip 83m, 8
A cord 84 consisting of lead wires t1 and t2 connected to 3b is drawn out, and can be freely connected to the terminal board of F, line, L, L, etc.

Therefore, if the above connection is made using the clips a3m and 83b and the rDIA CHECK j key 82 is pressed, the above judgment is made (through transmission/reception and calculation by the internal CPU 72), and the DP 77 performs the rHP DIA ABNORMALJ Since the display immediately indicates the performance deterioration of the barrier diaphragm S& of the high pressure chamber 42, it is possible to easily and accurately diagnose an abnormality in the barrier diaphragm 5a of the DPT 51 without preparing any special measuring equipment. will be carried out.

However, in addition to using barrier diaphragm 5a and sbt,
The same is true 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, and in some cases, (1)
, (The calculation of formula 111 is performed only on one side, and the diagnosis may be performed only on the diaphragm that is in contact with the fluid that affects the performance of the diaphragm, and only the initial value corresponding to this is stored in the memory.) You may.

9. The NVM 61 only needs to be attached to the DPT 51, and it is also possible to use other memory elements that can retain the contents for a long period of time.
30 CPU 55, or it may be performed by a CPU such as a control device, and the diagnosis results may be displayed on a separate display.The arrangement of the 5ps34 and TS35 is shown in FIG. Various modifications can be made, such as selection depending on conditions.

〔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. Significant effects can be obtained in diagnosis.

[Brief explanation of the drawing]

The figures show various embodiments of the present invention, in which Fig. 1 is a plan view of a composite sensor, Fig. 2 is a sectional view of a differential pressure transmitter, Fig. 3 is a schematic diagram of a differential pressure transmitter, and Fig. 4 is a circuit. A block diagram of the configuration, and FIG. 5 is an outline drawing of the portable tester. 5m, 5b・Working・Barrier diaphragm, T&. 7b, 131, 13b, 26...Communication hole, 8m, 8
b... Inner chamber, 9 O... Center diaphragm, 1
Qa, 1ib-... Filled liquid, 27... φψ composite sensor, 30... Pressure transmitter, 31... Board, 3
2...φ・Diaphragm, 33, 33a to 33d
-----DPS (differential pressure sensor), 34.34a~34
d...sps (static pressure sensor), 35...T
S (temperature sensor), 41φ...high voltage electric, 42...
・Low pressure chamber, 51...DPT (differential pressure transmitter), 55
．． 72...-CPU (processor). 59.78...ROM (fixed memory), 60°7
9--Salary/RAM (variable memory), 61-...NVM
(Non-volatile ordering memory), 58.75...cp (comparator), T1-...KB (keyboard), 17...
・DP (indicator), Ql, Ql・---TR () transistor), L, , L2e m @ @ line, 11.1
2... Lead wire, E-... Power supply. Figure 1 Figure 3 Figure 2

Claims (1)

[Claims] 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 are stored in a memory, A static pressure sensor that detects static pressure of at least one of the pressure transmitters 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 The compliance of at least one of the diaphragms is calculated using each detection output of the static pressure 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. A method for diagnosing diaphragm performance of pressure transmitters.