JPH0720800Y2 - Signal transmitter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a signal transmitter that converts a physical quantity such as a differential pressure or pressure into an electric signal and transmits the electric signal to a load as an output signal in a predetermined measurement range. Particularly, the present invention relates to a signal transmitter improved so that predetermined adjustment can be efficiently performed with a small number of buttons.

<Prior Art> FIG. 3 is a block diagram showing a configuration of a conventional two-wire signal transmitter.

Reference numeral 10 is a two-wire type signal transmitter that converts a physical quantity of a process variable (pressure, differential pressure, etc.) into an electric signal and transmits the electric signal. Electric power is supplied from a DC power source 11 through a load 12 and transmission lines l ₁ and l _2. Is supplied. The electric signal is transmitted as a current signal through the transmission lines l ₁ and l ₂ , and the voltage change occurring across the load 12 is detected to know the process variable.

The current signal is converted into a unified current of 4 to 20 mA by the two-wire type signal transmitter 10 set to a range corresponding to the pressure in the pipe, for example, and transmitted to the receiving instrument 13 on the load side, and is also displayed on the monitor, for example. Digitally displayed in 4 digits.

In this case, for example, when it is desired to change the pressure range, increase the current signal, or adjust the zero point, 2
It would be convenient if it could be operated from outside the wire-type signal transmitter 10.

Therefore, the handheld terminal 14 is connected to the transmission lines l ₁ and l ₂ by using the connection lines l ₁ ^- and l ₂ ^- as required, and the 2-wire type signal transmitter 10 is exclusively used for the handheld terminal 14. With the data communication function of the handheld terminal
Digital data such as parameter changes is transmitted from 14 to the two-wire signal transmitter 10.

Among them, the 2-wire type signal transmitter 10 is configured as follows.

SNR1 is a sensor that detects pressure / differential pressure and converts it into an electric signal. The converted analog signal is converted into a digital signal by the analog / digital converter A / D and stored in the memory MEM via the microprocessor μP1. Stored in the random access memory portion of the. The microprocessor μP1 uses the stored digital signal to execute a predetermined operation such as linearization according to the operation procedure written in, for example, the read-only memory portion of the memory MEM, and then performs the digital / digital operation.
It is output to the output circuit OPC via the analog converter D / A.

On the other hand, the predetermined calculation result in the microprocessor μP1 is digitally displayed on the built-in monitor LCD in the required number of digits.

The output circuit OPC digital / analog converter D / A transmission line to convert a voltage signal converted into an analog signal into a unified current signal I _L of 4~20mA at l _1, received via the l ₂ instrument 13 To transmit. Further, the output circuit OPC uses a part of the current signal I _{L to} generate a power source for the internal circuit of the two-wire type signal transmitter 10.

In this case, for example, a value corresponding to the current signal I _L is digitally displayed on the monitor LCD.

The IFC is an interface for data communication with the handheld terminal 14, is connected between the transmission lines l ₁ and l ₂ and the microprocessor μP ₁ , and converts digital signals from the transmission lines l ₁ and l ₂ into parallel data. Microprocessor μ
It has a function of transmitting to P1 and, conversely, transmitting the data from the microprocessor μP1 as a serial signal to the transmission lines l ₁ and l ₂ .

Next, the handheld terminal 14 is configured as follows.

SER is a setting device operated by an operator and has a built-in monitor. Various settings or requests such as model request of 2-wire type signal transmitter 10, display resolution change, range change, zero point adjustment, abnormality detection, or current signal I _L value display can be made. .

μP ⁻ is a microprocessor, for example, the data from the setter SER is input, and the digital signal is sent to the 2-wire type signal transmitter 10 via the interface IFC ⁻ according to the processing procedure stored in the memory MEM ^−. To do. The microprocessor .mu.P ^- the response data from the signal transmitter 10 of the two-wire Interferon chair IFC ^- the uptake, further memory MEM ^{- -} memory MEM via the decrypted according stored in the processing procedure, setter Display on SER monitor.

However, since such a signal transmitter 10 does not have a zero adjustment function or a fine adjustment function (INC / DEC) for the current signal I _L , the signal transmitter installed in the field.
There was an inconvenience that it was not possible to execute zero adjustment or fine adjustment of the current signal I _L with only 10.

On the other hand, the signal transmitter shown in FIG. 4 can perform zero adjustment or fine adjustment of the current signal I _{L by} itself. This will be described below.

The signal transmitter 15 receives a high pressure P _H and a low pressure P _L , detects a differential pressure ΔP between them and converts the electric signal into an electric signal SNR2, and outputs the electric signal after converting the electric signal into a predetermined measurement range. And a conversion unit CNV for converting.

The body 16 of this conversion unit CNV has a cylindrical shape,
A detector SNR2 is fixed to one end of the cylinder, and a lid 19 having a transparent window 17 and an ammeter 18 is screwed into the center of the other end. On the right side surface of the body 16, a terminal casing 20 that houses terminals for connecting signal lines or power supply lines is fixed.
A switch box 21 containing a pushbutton switch is fixed to the left side surface of the body 17.

In addition, a terminal plate 22 is provided on the end surface of the body 16 facing the transparent window 17.
Is fixed, and a mode selector switch 23 for switching various functions is fixed to a part of this.

Further, the switch box 21 accommodates two switches, an increase switch 24 for increasing the current signal and a decrease switch 25 for decreasing the current signal.

With such a configuration, when the output current signal is increased or decreased, the switch box 21 may be opened and the increase switch 24 and the decrease switch 25 may be pressed to increase or decrease respectively.

However, when the zero adjustment is performed so that the current signal becomes zero when the differential pressure is zero, the lid 19 is opened and the mode selector switch 23 is set to the zero adjustable state, and then the increase switch 24 and the decrease switch 25 are set. Press to execute zero adjustment.

<Problems to be solved by the invention> However, in such a conventional signal transmitter, the lid 19 must be opened when the zero adjustment function is selected, and the mode changeover switch 23 is in what state in a normal use state. There is an inconvenience that causes an erroneous operation because it is not known whether or not it is.

<Means for Solving the Problems> In order to solve the above problems, the present invention calculates a measurement range by a microcomputer from the difference between a low range value and a high range value that are set by converting a physical quantity into an electric signal. In a signal transmitter for transmitting to a load as an output signal corresponding to a physical quantity, INC means for increasing an output signal by increasing a low range value by a microcomputer using an increase signal generated by pressing a first button; DEC means for reducing the output signal by reducing the low range value by the microcomputer using the decrease signal generated by pressing the button, and detection when the physical quantity is set to zero by pressing the first and second buttons at the same time And a one-push zero means for adjusting the difference between the zero signal and the low range value to 0%. The first button and the second button are attached to the signal transmitter itself.

<Operation> When increasing or decreasing the output signal, the first button or the second button is pressed to adjust the increase or decrease of the output signal.

In addition, when the output signal does not become zero% when the physical quantity is zero, the zero adjustment for adjusting this to zero is automatically adjusted to the zero point by pressing the first button and the second button at the same time.

<Embodiment> An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing one embodiment showing the configuration of the present invention. It should be noted that parts having the same functions as conventional functions are designated by the same reference numerals, and appropriate description thereof will be omitted.

Reference numeral 26 is a signal transmitter, which has a detector SNR3 inside and a vibration type sensor incorporated therein, which converts a physical quantity such as a differential pressure or pressure into a frequency signal f for conversion / drive circuit.
Send to 27.

The conversion / drive circuit 27 forms an oscillation circuit together with the detector SNR3 and converts the input frequency signal f into a digital signal DS. This digital signal DS is the microprocessor μP2
It is stored in a predetermined area of the random access memory of the memory MEM under the control of.

This stored digital signal DS is the microprocessor μ
The microprocessor μP2 performs a predetermined calculation according to a calculation formula that is read by P2 and stored in advance in the read-on memory of the memory MEM, such as a calculation that converts this digital signal into a predetermined measurement range or a calculation of linearity. It is executed and output to the output circuit OPC via the digital / analog converter D / A.

This measurement range SPAN is determined by externally setting the Loreher value LRV and the high level value HLV in advance.

The measurement range S is applied to this microprocessor μP2 by pressing (ON) this switch SW1.
An increase signal INC that increases the PAN low-range value LRV is input. From switch SW2, switch SW2
The decrease signal DEC that decreases the low range value LRV by pressing (ON) is input.

Measurement range is increased by increasing signal INC and decreasing signal DEC generated by pressing switches SW1 and SW2.
A calculation procedure for increasing or decreasing the low range value LRV of SPAN is stored in the memory MEM.

The microprocessor μP2 increases or decreases the low range value LRV according to these calculation procedures, and outputs it to the output circuit OPC via the analog / digital converter A / D to output the current signal.
Increase or decrease I _L.

When these switches SW1 and SW2 are turned on at the same time, the microprocessor μP2 detects the increase signal INC and the decrease signal DEC and the microprocessor μP2 adjusts the zero according to the zero adjustment program stored in the memory MEM. Run automatically.

Next, the operation of the embodiment configured as described above will be described with reference to the flow chart shown in FIG.

In step (a), the physical quantity, for example, the differential pressure is made zero, and in step (b), this differential pressure is detected.

In step (c), one-push zero is executed.
This one-push zero is executed by turning on the switches SW1 and SW2 at the same time, and when they are off, this step is skipped and the process proceeds to step (e).

By simultaneously turning on the switches SW1 and SW2, the difference Δ between the low range value LRV set from the outside and the differential pressure input in the step (b) state is detected.

If this difference Δ is not zero, zero adjustment for correcting this difference is set in step (d).

In step (e), zero adjustment is performed using the set zero adjustment amount.

In step (f), when one of the switches SW1 and SW2 is turned on and the increase signal INC or the decrease signal DEC is sent to the microcomputer μP2, the process proceeds to step (g) to determine the increase amount or the decrease amount. In this case, the span value does not change.

At the step (h), the low level value LRV and the high level value HRV are set by using these increasing or decreasing amounts.

In step (li), scaling is executed. Here, if the differential pressure is ΔP, this is (ΔP-LRV) / (HRV-LR
Scaling as V).

After that, in step (nu), it is converted into the corresponding current signal and displayed on the LCD.

The above procedure of differential pressure detection → zero adjustment → scaling → output (current signal) is repeatedly executed, for example, every 250 ms by the timing signal obtained by dividing the frequency of the built-in crystal. Also, when switches SW1 and SW2 are turned on, LR
The output current value can be set by changing the values of V and HRV → scaling → output (current signal).

<Effects of the Invention> As described above in detail with reference to the embodiments, according to the present invention, the signal transmitter itself is provided with the first and second switch means, and these two switches are turned on. By combining ON / OFF, it is possible to realize three functions of one-push zero adjustment in addition to increasing and decreasing the output current, so it is necessary to open the lid each time the adjustment function is changed as in the past. In addition, since the states of the two switches to be operated can always be visually observed, the operation is simple and erroneous operations can be eliminated, which also contributes to a reduction in manufacturing cost.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, and FIG.
FIG. 1 is a flow chart showing the flow for explaining the operation of the embodiment shown in FIG. 1, FIG. 3 is a block diagram showing the configuration of a conventional signal transmitter, and FIG. 4 is a configuration of another conventional signal transmitter. It is a block diagram shown. 10 …… 2-wire type signal transmitter, 11 …… DC power supply, 12 …… load, 13 …… receiver, 14 …… handheld terminal,
15, 26 ...... Signal transmitter, 19 ...... Lid, 21 ...... Switch box, 23 ...... Mode changeover switch, 24 ...... Increase switch, 25 ...... Decrease switch, 27 ...... Conversion / drive circuit, MEM
...... Memory, μP1, μP2 …… Microprocessor, SW
1, SW2 …… switch, SNR1 to SNR3 …… detector.

Claims (1)

[Scope of utility model registration request] 1. A signal transmitter for converting a physical quantity into an electric signal, calculating a measurement range from a difference between a set low range value and a set high range value, and transmitting it to a load as an output signal corresponding to the physical quantity, First
INC means for increasing the output signal by increasing the low range value by the microcomputer using an increase signal generated by pressing a button, and by the microcomputer using a decrease signal generated by pressing a second button DEC means for decreasing the output signal by decreasing the low range value, a zero signal detected when the physical quantity is set to zero by simultaneously pressing the first button and the second button, and the low range value And a one-push zero means for adjusting the difference between the two to 0%, wherein the first button and the second button are attached to the signal transmitter itself.