JP2012026778A - Remaining power detection method and remaining power detection device for primary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a remaining power detection method and remaining power detection device capable of accurately predicting remaining power of a battery in a field apparatus employing a primary battery.SOLUTION: A load is connected to a primary battery which is mounted in a field apparatus subjected to data collection through a radio means for a predetermined time and in a predetermined cycle, and then released. On the basis of a time until a recovery from a battery voltage of the primary battery under the load connection to a battery voltage of the primary battery under the load release, remaining power of the primary battery is determined.

Description

  The present invention detects the remaining amount of primary batteries mounted in field devices such as pressure / differential pressure transmitters, various flow meters, thermometers, valve positioners, etc. that are distributed in plants, factories, etc. and collect data by wireless means. The present invention relates to a method and a remaining amount detection device.

  In a general field device, it is connected to a control computer system installed at a higher level by a two-wire signal line, etc., and transmits and receives a 4-20 mA current signal, thereby generating a power supply and collecting collected data at a higher level. Send to.

  In recent years, there is also a system that incorporates wireless means into a field device and transmits detected and collected data to a host device such as a control computer system. Prior art documents related to such a field device include: There are Patent Document 1 and Patent Document 2.

  FIG. 5 is a functional block diagram illustrating a configuration example of a field device including wireless means. The process pressure P is input to the vibration type sensor drive units 1A and 1B, detected, amplified and shaped as the natural frequency of the vibration type sensor, and input to the CPU 2 as a pulse signal. The CPU 2 is a macro processor having a frequency counter and a digital analog circuit.

  The natural frequency (resonance frequency) of the sensor is calculated from the counted number of pulses, and the process pressure P is calculated from the value. The calculation result is transmitted as a communication signal corresponding to the process pressure through the RF module 3 via the antenna 4 to the host device that collects data.

  The display device 5 is an external display function such as an LCD, and can display process pressures and alarms periodically. The RAM 6 and the EEPROM 7 store a correction coefficient when the CPU 2 calculates the process pressure P, an intermediate value of the process pressure, and life management data of the primary battery 8.

  In field devices using radio, a method of operating with a primary battery is common. In the case of using a battery, in order to save the trouble of replacement, a power saving operation such as an intermittent operation is performed, and an operation for several years is required. Therefore, a lithium thionyl chloride battery having a characteristic that the self-discharge is extremely small is used as the primary battery.

  The lifetime of the built-in primary battery 8 is managed by the CPU 2. There is a technical disclosure in Patent Document 3 as a method for managing the life of a primary battery. FIG. 6 is a functional block diagram showing an embodiment of a conventional primary battery remaining amount detection device disclosed in Patent Document 3. In FIG.

  When a constant load 40 is connected from the CPU 20 via the electronic switch 30 to the primary battery 10 at regular intervals, the battery voltage V at the time of connection is read by the CPU 20, and the load is connected from a preset reference voltage When the voltage V decreases, it is determined that the battery life has come to an end.

  FIG. 7 is a change characteristic diagram of the battery voltage when the pulse current I by the load flows. The battery voltage Vr, which decreases when the pulse current I flows, is compared with the threshold value Vs, and when Vr is lower than Vs, a battery life alarm is raised.

JP 2003-134030 A JP 2003-134261 A JP 2007-280935 A

The prior art has the following problems.
(1) Due to its characteristics, the primary lithium battery maintains a constant voltage until there is no electrode material, and becomes almost 0 V as soon as it disappears. When measuring the battery voltage and calculating the service life, even if a battery replacement alarm is issued, the battery voltage drops rapidly, so the time until battery replacement is short, replacement is not in time, and troubles such as system down are caused. appear.

(2) In addition, it is difficult to distinguish between new and old batteries due to their characteristics. If a worker re-installs a once removed battery, it will be detected as a new battery, and the battery life time will be incorrectly calculated. appear.

(3) In the technique described in Patent Document 3, there is a possibility that the voltage is lower than the voltage at the time of discharging in a normal operation due to the internal impedance of the battery. In addition, when the battery voltage falls below the reference value, the lifetime is determined for the first time, and it is impossible to make a prediction until the battery replacement timing. As a result, a system failure occurs due to the battery voltage drop.

(4) When a field device having a wireless means returns data transmission with reception from the outside, when the pulse current for wireless transmission / reception work and diagnosis overlaps, the wireless is added to the pulse current I. The operating current of the means will also flow.

  FIG. 8 is a change characteristic diagram of the battery voltage when the transmission unit is activated when a pulse current is generated by the load. When there is a reception request from the outside, since the device cannot determine where the wireless operation enters, when a pulse current flows as in the wireless operation, the consumption current depends on the battery impedance and the battery voltage Vr. As a result, the voltage is further lowered to Vr ′, which is lower than the threshold value Vs, which may cause erroneous detection.

  An object of the present invention is to provide a remaining amount detection method and a remaining amount detection device capable of accurately predicting a remaining amount of a battery in a field device using a primary battery.

In order to achieve such a subject, the present invention has the following configuration.
(1) A primary battery mounted on a field device that collects data by wireless means is opened after connecting a load for a predetermined period at a predetermined period, and the load is determined from the battery voltage of the primary battery when the load is connected. A method for detecting a remaining amount of a primary battery, comprising: determining a remaining amount of the primary battery based on a time until the battery voltage of the primary battery is recovered when the battery is opened.

(2) When the difference voltage between the voltage of the primary battery when the load is connected and the voltage of the primary battery when the load is released is 100% span, the voltage of the primary battery when the load is connected The method for detecting a remaining amount of a primary battery according to (1), wherein a time required for recovery from approximately 20% to approximately 80% of the span is measured.

(3) The remaining primary battery according to (2), further comprising: a ROM that holds a remaining battery level as a reference value for a time required for the battery voltage to recover from approximately 20% to approximately 80% of the span. Quantity detection method.

(4) The method for detecting the remaining amount of the primary battery according to (3), wherein the reference value of the ROM is corrected based on a temperature measurement value of the primary battery.

(5) The wireless means that is periodically driven serves as a load on the primary battery, and the remaining capacity of the primary battery is determined based on a battery voltage recovery characteristic of the primary battery when the load is released after a predetermined time. The method for detecting a remaining amount of a primary battery according to any one of (1) to (4).

(6) In any one of (1) to (5), an alarm display or an alarm is transmitted to the host device by the wireless means when the determination value of the remaining amount of the primary battery exceeds a predetermined threshold value The primary battery remaining charge detection method as described.

(7) Load control means that opens after connecting a load for a predetermined period of time with respect to a primary battery mounted on a field device that collects data by wireless means, and a battery voltage of the primary battery when the load is connected To measure the time until the battery voltage of the primary battery recovers when the load is released, and the remaining battery capacity for determining the remaining capacity of the primary battery based on the measured time A primary battery remaining amount detection device comprising: a determination unit.

According to the present invention, the following effects can be expected.
(1) Even if the internal impedance of the battery is lower than the voltage at the time of discharging during normal operation, there is no possibility of mistaking the battery life. Further, it is possible to make a prediction up to the timing for battery replacement with high accuracy, and it is possible to avoid a system failure.

(2) Even if a product such as a field wireless device has a major problem due to a drop in the battery voltage, a battery replacement alarm is issued in advance by accurately predicting the remaining battery level to avoid trouble. can do.

It is a functional block diagram which shows one Example of the residual amount detection apparatus of the primary battery to which this invention is applied. It is a recovery characteristic figure of the battery voltage of the primary battery after releasing from load. It is a table | surface which shows the required time from 20% of spans to 80% read from the characteristic view of FIG. It is a flowchart which shows the process sequence of the residual amount detection method of the primary battery of this invention. It is a functional block diagram which shows the structural example of the field apparatus which comprises a radio | wireless means. It is a functional block diagram which shows one Example of the residual amount detection apparatus of the conventional primary battery. It is a change characteristic figure of a battery voltage when the pulse current by a load flows. It is a change characteristic figure of a battery voltage when a transmission means operates at the time of pulse current generation by load.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a functional block diagram showing an embodiment of a primary battery remaining amount detection apparatus to which the present invention is applied. The same elements as those in the conventional configuration described with reference to FIG.

  In FIG. 1, the element added to the conventional configuration of FIG. 6 is a temperature sensor 50. A feature of the present invention resides in a data processing method in the CPU 20. The electronic switch 30 is ON / OFF controlled by an operation signal from the IO port 21 of the CPU 20, and the load 40 is connected to the primary battery 10 for a predetermined time at a predetermined cycle.

  The voltage V of the primary battery 10 is guided to the CPU 20 and is always digitally converted by the A / D converter 22. The internal counter 23 gives a trigger signal to the A / D converter 22 and stores the digital conversion value of the A / D converter 22 at a predetermined time interval in the RAM 24. The ROM 25 stores a life prediction reference value, and this life prediction reference value is corrected by the temperature measurement value from the temperature sensor 50.

  FIG. 2 is a recovery characteristic diagram of the battery voltage of the primary battery after being released from the load. FIG. 2A is a recovery characteristic diagram in which the remaining battery level is equivalent to 90%. The gradient of the rising curve from the battery voltage VL when the load is connected to the recovery voltage VH after the load is released is denoted by α1.

  FIG. 2B is a recovery characteristic diagram in which the remaining battery level is equivalent to 27%. The gradient of the rising curve from the battery voltage VL when the load is connected to the recovery voltage VH after the load is released is denoted by α2. α2> α1, and the gradient increases in proportion to the remaining battery level.

  A feature of the present invention is that the remaining battery level is calculated based on the slope of the rising curve up to the recovery voltage after the load is released. As shown in FIGS. 2A and 2B, the specific signal processing spans the difference voltage between the voltage VL of the primary battery when the load is connected and the voltage VH of the primary battery when the load is released. When 100%, the elapsed time T1 and T2 required from the time t1 when the voltage VL of the primary battery when connected to the load is recovered to approximately 20% of this span to the time t2 when the recovery is approximately 80% is measured. A reference value of the battery remaining amount with respect to the elapsed time is read from the table of the ROM 25 to predict the battery remaining amount.

  FIG. 3 is a table showing the required time from the span of 20% to 80% read from the characteristic diagram of FIG. According to this table, when the remaining battery level is 90%, the required time from the span 20% to 80% is 48.81 seconds. On the other hand, when the battery remaining amount is 27%, the required time from the span 20% to 80% is 44.32 seconds.

  Since the primary battery 10 has a difference in the slope α of the rising curve depending on the temperature, the life expectancy can be accurately predicted by correcting the reference value held in the ROM 25 in the CPU 20 by the measured value of the temperature sensor 50. Is realized.

  FIG. 4 is a flowchart showing a processing procedure of the primary battery remaining amount detection method of the present invention. When the process starts in step S1, temperature data is acquired in step S2. Next, in step S3, a load is applied to the primary battery for a predetermined period. If it is determined in step S4 that the load connection is completed, the counter is started in step S5, and the counter is cleared in step S6.

  In step S7, AD conversion data is stored in the RAM in step S8 from the timing when the counter reaches Ams in step S7. This data storage is continued until Bsec elapses in the check in step S9, and the process proceeds to step S10. Here, A and B are arbitrary numerical values.

  In step S10, the required time from 20% to 80% when the load is released is obtained from the AD conversion data stored in the RAM. In step S11, the reference value in the ROM is corrected by temperature.

  In step S12, a predicted life of the primary battery is calculated by comparison with a temperature-corrected ROM reference value. If it is determined in step S13 that the predicted life is less than the alarm threshold value, an alarm is reported on the wireless communication and device display device in step S14, battery replacement is prompted, and the process ends in step S15. If it is determined in step S13 that the predicted life is greater than the alarm threshold, the process skips to step S15 and ends.

  In the configuration in which the field device includes wireless means, the wireless means that is periodically driven for a predetermined time becomes a load of the primary battery, so that the battery voltage recovery characteristics of the primary battery when transmission is stopped and the load is released It is possible to make the specification for determining the remaining amount of the primary battery based on the above.

  The reference value set in the ROM 25 in the CPU 20 may be corrected by the average environmental temperature. Further, when the user replaces the battery, in order to determine whether the battery is new or old, the remaining amount determination of the present invention may be executed first when the battery is inserted.

10 battery 20 CPU
21 IO port 22 A / D converter 23 Internal counter 24 RAM
25 ROM
30 Electronic switch 40 Load 50 Temperature sensor

Claims (7)

  For a primary battery mounted on a field device that collects data by wireless means, the load is released after connecting a load for a predetermined period at a predetermined cycle, and the load is released from the battery voltage of the primary battery when the load is connected. A method for detecting a remaining amount of a primary battery, comprising: determining a remaining amount of the primary battery based on a time until the battery voltage of the primary battery is recovered.   When the difference voltage between the voltage of the primary battery when the load is connected and the voltage of the primary battery when the load is released is 100% of the span, the span is more abbreviated than the voltage of the primary battery when the load is connected. 2. The method for detecting the remaining amount of a primary battery according to claim 1, wherein a time required for recovery from 20% to approximately 80% is measured.   The primary battery residual quantity detection method according to claim 2, further comprising: a ROM that holds a residual battery quantity as a reference value for a time required for the battery voltage to recover from about 20% to about 80% of the span. .   The method for detecting the remaining amount of the primary battery according to claim 3, wherein the reference value of the ROM is corrected based on a temperature measurement value of the primary battery.   The wireless means that is periodically driven becomes a load of the primary battery, and the remaining capacity of the primary battery is determined based on a recovery characteristic of a battery voltage of the primary battery when the load is released after a predetermined time. A method for detecting a remaining amount of a primary battery according to claim 1.   6. The primary battery according to claim 1, wherein an alarm display or an alarm is transmitted to a host device by the wireless means when a judgment value of the remaining capacity of the primary battery exceeds a predetermined threshold. Remaining amount detection method.   For a primary battery mounted on a field device that collects data by wireless means, a load control means that opens after connecting a load at a predetermined cycle for a predetermined time, and a battery voltage of the primary battery when the load is connected, Time measuring means for measuring the time until the battery voltage of the primary battery recovers when the load is released; battery remaining capacity determining means for determining the remaining capacity of the primary battery based on the measured time; A remaining amount detection device for a primary battery, comprising: