JP2598352B2 - measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring apparatus which is used in a process control apparatus or the like and needs to correct measured values depending on environmental conditions.

[0002]

2. Description of the Related Art Generally, a process control device converts a physical quantity detected by a sensor provided at a site into an electric signal,
It is transmitted to a place where a monitoring device is provided through a two-wire transmission line to perform measurement. In this case, in this case, if the measurement target is, for example, a differential pressure type flow meter using an orifice, a mass flow rate cannot be obtained only by the measurement result,
Corrections must be made with the temperature and pressure data of the fluid. For this reason, conventionally, temperature data and pressure data were also measured at the same time, and the data were sent to the monitoring device via separately prepared transmission lines, and the monitoring device performed a correction operation.

[0003]

However, providing a dedicated transmission line for correction data is very inefficient, and only the differential pressure flow rate measurement is performed when the equipment is first introduced.
Even if an attempt is made to install a transmitter for correction when high-precision measurement is required, it is not easy to add a transmission line at that time, and there is a problem that it is difficult to make a stepwise improvement.

[0004]

SUMMARY OF THE INVENTION In order to solve such a problem, the present invention provides a main transmitter for transmitting a physical quantity to be measured to a transmission line at a predetermined timing, and an environment in which the main transmitter is located. physical measurement target transmitted from the main transmitter detects the physical quantity of the measurement value correcting determined by conditions
A sub-oscillator is provided for detecting a quantity from a transmission path and sending a physical quantity for correcting a measured value to the transmission path at a timing at which the quantity does not collide with a physical quantity to be measured .

[0005]

The data of the sub-oscillator is transmitted at a timing when the data of the main oscillator is not transmitted, so that one transmission path can be shared for both data.

[0006]

FIG. 1 is a circuit diagram showing an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a main oscillator for detecting a physical quantity to be measured and sends it out at a predetermined period;
A sub-oscillator that detects a physical quantity for measurement value correction determined by the environmental conditions in which it is placed and sends the detected physical quantity at a timing that does not collide with a signal sent from the main oscillator 1, and 5 is a signal from each oscillator. A transmission line 6 for transmitting a signal is a monitoring device for detecting a signal transmitted via the transmission line 5.

Each transmitter can receive the output of another transmitter as a voltage change. Each transmitter has a specific address, and when outputting a signal, the address and data are output as a pair. The address is assigned to each transmitter so that it starts from 0 and ends with N, and the main transmitter 1 is assigned an address of 0. Then, for example, after the transmitter of the address B outputs, the transmitter of the address C having one address larger than that of the address is set to output after a certain time t1. However, after the transmitter at address N, the main transmitter 1 at address 0
Is output.

[0008] For example, the transmitter of the address D, which has two more addresses than the transmitter of the address B, outputs the signal of the address B and outputs the signal of the address C within a predetermined time t2. When the transmitter at the address C does not output within t3, the output is transmitted. Similarly, the transmitter of the address E outputs an output when the transmitters of the addresses C and D do not output within a predetermined time t3 after the output of the address B. However, it is set so that t3> t2. In this way, operation is possible without transmitters corresponding to all addresses.

FIG. 2 illustrates the above.
In FIG. 2, (a) is address 0, (b) is address 1, (c)
Is address 2. (d) shows the output timing of the transmitter at address 3, where all the transmitters send signals from address 0 to address 3 in the first cycle, while the transmitters at addresses 1 and 2 transmit the next cycle. This shows a state in which no signal is transmitted.

When returning from the last address (address 3 in this example) to address 0, the signal is returned to address 0 at a value of a sufficiently longer interval than a normal signal interval. At this time, a signal may be transmitted to this portion (the portion indicated by the symbol t4 in FIG. 2). The signal shown in FIG. 2D is expanded and inserted in the period t4.

The transmitter constructed as described above can transmit the measurement data and the correction data on the same transmission line by attaching a sub-transmitter as required. The correction calculation may be performed based on Further, the correction calculation may not be performed by the monitoring device 6 but may be performed by any one of the plurality of transmitters.
In addition, the present invention is not limited to the correction operation, but connects the same type of transmitter, outputs an average by the operation unit, and outputs 2 out of 3
For performing (2 out of 3) and measuring the liquid level and interface of the tank, it can be used to measure the temperature and pressure in the tank to perform density correction.

[0012]

As described above, according to the present invention, the signal for correction is transmitted from the sub-oscillator to the same transmission line as the main oscillator at the timing that does not collide with the output of the main oscillator, so that economic efficiency is improved. This has the effect that highly accurate measurement can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a time chart illustrating signal transmission timing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Oscillator 2 Oscillator 3 Oscillator 4 Oscillator 5 Transmission line 6 Monitoring device

Claims (1)

(57) [Claims] 1. A measuring apparatus in which a physical quantity to be measured is transmitted by a transmission line and a true value needs to be obtained by correcting a value detected according to an environmental condition in which the physical quantity is placed. A main transmitter for transmitting a predetermined timing to a transmission line, and detecting a physical quantity for measurement value correction determined by an environmental condition in which the main transmitter is placed, and measuring a physical quantity of a measurement target transmitted from the main transmitter. Detected from the transmission line and measured
For correction of measured values at a timing that does not collide with the physical quantity to be fixed
And a sub-oscillator for transmitting the physical quantity of (1) to the transmission path .