JPH03204800A - Measuring device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a measuring device used for differential pressure/pressure gauges, flow meters, liquid level gauges, thermometers, and the like.

[Prior Art] In recent years, sensors used in process control devices convert a state quantity into an output current of 4 to 20 A and transmit the state change at a detection point to the receiving side. Some devices have a constant current mode in which a constant value of current, for example 50% or 75% of full scale, is supplied to the transmission line.

This is a function to check whether there are any abnormalities such as disconnections in the wiring between the sensor and receiver, to check the operation of the receiver, to check the accuracy of the receiver, etc. Since comprehensive confirmation is possible, it is useful as a regular maintenance check item.

[Problem to be solved by the invention] However, while such a function is convenient, if the input value of the system is a stable constant value, it may be difficult to determine whether the receiving side is in measurement mode or constant current mode. Since it is difficult to tell the difference, there are cases where it is misunderstood that measurement is in progress even though it is in constant current mode, leading to incorrect recording or control, which may have an inconvenient effect on the production process.

In order to avoid misunderstandings, it is conceivable to set a measurement mode return time for forcibly transitioning to the measurement mode after a certain period of time has passed since the constant current mode has been entered. However, with this method, it is difficult to set a fixed time because the time required to check the actual receiver operation and accuracy varies widely. It is also possible to set the return time as a changeable value from an external interface, etc., but this would complicate the configuration procedure for the entire transmitter (which converts the sensor output into a current of 4 to 20 mA). There was a problem with system compatibility as it became necessary to negotiate data transmission procedures with external interfaces.

[Means for Solving the Problems J] In order to solve these problems, the present invention includes means for generating output changes in a predetermined pattern at predetermined time intervals.

[Effect] Predetermined output changes occur automatically at predetermined time intervals.

[Example] FIG. 1 is a diagram showing an example of a pattern generated by the present invention. For example, as shown in FIG. This outputs a signal with a constant value of .

This time interval needs to be an appropriate time that allows the receiving side to recognize that it is not in the measurement mode, and for example, a value of about 10 seconds is appropriate as in this example.

Similarly, the output change needs to have a pattern that allows the receiver to recognize that it is not in measurement mode.

For this reason, for example, as shown in the figure, a value representing about 10% of the full scale can be considered.

FIG. 1(b) shows another example of the pattern, in which a signal whose positive and negative amplitudes change by about 10% of the full scale is periodically generated by about 2 degrees every 10 seconds.

This is a flowchart of the device for generating this signal in FIG. For example, the judgment is made based on whether or not a flag is set.

When it is determined that it is time for the measurement mode in step 101, a predetermined constant value is output for 2 seconds as shown in step 102. and 1 in step 103
It is determined whether 0 seconds have elapsed. If 10 seconds have not elapsed, check the flag indicating whether or not it is in measurement mode, and if it is still in constant current mode, proceed to step 102.
Continue. If a command to cancel the constant current mode is given by an external setting device or the like and the constant current mode is no longer in effect (that is, if it is in the measurement mode), the process returns to step 100 and the normal measurement state is entered.

Further, if the flag does not change and remains in the constant current mode, pattern change processing is performed as shown in step 105 when the flag changes for 10 seconds. Flow then returns to step 102.

[Effects of the Invention] As explained above, the present invention includes a means for generating output changes in a predetermined pattern at predetermined time intervals, so that it is possible to reliably distinguish between the measurement mode and the constant current mode. This method has the effect of preventing damage in the manufacturing process due to data discrepancies, since it does not make erroneous decisions as in the conventional method.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a generated pattern, and FIG. 2 is a flowchart showing the operation of the means for generating the pattern.

Claims (1)

[Claims] A measuring device that has the function of transmitting a state quantity detected by a sensor to a receiver side, and also transmitting a constant transmission output to a transmission path in order to confirm that signal transmission is being performed reliably. A measuring device comprising means for generating output changes in a predetermined pattern at predetermined time intervals.