GB2090088A

GB2090088A - Physical Variable Monitor

Info

Publication number: GB2090088A
Application number: GB8041262A
Authority: GB
Original assignee: VICKERY ANDREW CHARLES
Current assignee: VICKERY ANDREW CHARLES
Priority date: 1980-12-23
Filing date: 1980-12-23
Publication date: 1982-06-30

Abstract

A monitor receives consecutive digital signals (at 11) representative of the value of a variable such as temperature, voltage, current or pressure, at predetermined time intervals, and temporarily stores the digital signals (at 13). A central processor unit (14) calculates, under control of an EPROM (15) the mean of a number of consecutive stored signals and compares the mean with a previously calculated mean to determine whether the calculated mean differs from the previously calculated mean to more than a predetermined extent. A clock (16) is provided, and a storage means (13) stores the calculated mean signal when it so differs together with the clock signal. The task of monitoring a physical variable, for example the progress of a number of batteries under charged, is thereby made more efficient. <IMAGE>

Description

SPECIFICATION Physical Variable Monitor This invention relates to apparatus for monitoring a physical variable such as temperature, voltage, current or pressure.

A physical variable is typically sensed by a sensor which generates an analog electrical signal representative of the instantaneous value of the variable together with extraneous physical and electrical interference, ripple effects and other noise. The signal is commonly employed to position a pointer on a dial, i.e. an analog display.

A disadvantage of such systems is that a human operator must be continuously present to monitor the instantaneous pointer position.

With the advent of general data processing systems it has become possible for raw data, such as the above analog signals, to be processed and displayed in almost any specified format. Such systems together with their software can be expensive. Moreover they are not adapted to the specific application of monitoring a physical variable. Thus an analog signal directly representative of a sensed physical variable will, firstly, inevitably be accompanied by noise as described above and, secondly, its accuracy will be a function of the sensitivity of the original sensor and the use to which the monitored signal is to be put. These practical characteristics render the use of general data processing equipment inefficient for this task.

An object of the present invention is to provide a monitor suited to the specific task of monitoring a signal representative of a physical variable.

According to the present invention there is provided a physical variable monitor comprising: means for receiving consecutive digital signals representative of the value of a physical variable at predetermined time intervals; memory means for temporary storage of said digital signals; processor means for calculating the mean of a predetermined number of consecutive said temporarily stored signals and comparing said mean with a previously calculated said mean to determine whether said calculated mean differs from said previously calculated mean to more than a predetermined extent; clock means; and means for storing said calculated mean signal when it so differs and for simultaneously storing a clock signal.

The processor means may comprise a microprocessor, and the monitor conveniently includes an analog to digital converter for receiving analog input signals from a physical variable sensor and converting the analog input signal into said consecut ve digital signals.

The comparing means may be adapted to permit adjustment of said predetermined extent of difference between successively calculated said means signals.

A printer may be provided either incorporated with the apparatus or adapted for selective connection thereto. The apparatus may then be activated when desired to cause the printer to print out a stored calculated mean signal and its associated clock signal. The apparatus may be arranged to print out the stored signals substantially immediately, or may be arranged to store said signals for print out at a later time upon demand.

The monitor may be provided with means for generating an alarm signal or a control signal or both upon occurrence of a predetermined event, for example when the digital input signal exceeds a threshold or when the rate of change of the input signal exceeds a preset rate.

An embodiment of the invention will now be described, by way of example, with reference to the single Figure of the accompanying drawing.

The drawing is a block circuit diagram of a battery charging monitor. A physical variable sensor in the form of a voltmeter (not shown) is connected across a battery being charged by a battery charge (not shown). The sensed voltage is reduced by a potential divider and applied as an analog input to a free-running 1 2-bit analog to digital converter 10 with a conversion limit of, e.g., 21 milliseconds. The resulting digital signals are supplied to an 8-bit parallel input/output (PIO) port means compatible with the standard Intel Z 80 microprocessor.

The received digital signals are transferred on a data bus 12 to a temporary storage means 13 under control of a central processing unit (CPU) 14 suitably an Intel Z 80 8-bit microprocessor.

The temporary storage suitably comprises 2K bytes of static random access memory (RAM) 13.

The CPU operates under control of an operating programmeentered into an externally programmable read only memory (EPROM) 15 of, e.g., 2K bytes capacity.

An arithmetic logic unit in the CPU 14 calculates the mean of a predetermined number, e.g. 3, of consecutive temporarily stored signals in the RAM 13. This serves to reduce the effects of the inevitable noise accompanying the input signals, e.g. interference and ripple effects. The CPU then compares the calculated mean with the next previously calculated said mean to determine whether said calculated mean differs from the previous mean to more than a predetermined extent, which may be an increase or a decrease.

A real time clock signal is made available in the RAM through the CPU by means of a 2 MHz crystal oscillator 16 connected through a divider 1 7 to a non-maskable interrupt (NMI) of the CPU.

The RAM 13 stores each said calculated signal which differs by more than said extent together with the associated clock signal.

A second 8-bit parallel input/output (PIO) compatible port means is provided. The port means 18 is provided with monitor control elements, e.g. start, list and continuous print switches, a unit running lamp, and a control terminal suitable for connection to a contactor of the battery charger control circuit. A printer (not shown) may be permanently connected to the port means 18. Alternatively the printer may be a separate unit provided with a lead and connector 19 for connection to the port means 18.

When the printer is integral or connected, it operates to print out a stored calculated mean signal and its associated stored clock signal from the RAM 13. When the continuous print switch is operated the printer prints each pair of signals as they arrive. When the list switch is operated the printer prints out all the stored pairs of signals since the start switch was last operated to start the monitor. It will be appreciated that a number of batteries may be set up for charging (a process that takes a number af hours) and each connected to a monitor as described and illustrated herein. A single separate printer may then be connected in succession to each monitor to list the stored signal pairs from each monitor. Those lists provide the essential information necessary to monitor the progress of all the batteries under charge.

The stored programme in the EPROM 15 may also provide for particular predetermined comments to be printed by the printer when the stored signals attain particular preset values, e.g.

to indicate the phase of the battery charging cycle (e.g. "gas", "bulk charge complete", "equalizing complete", "contactor-out").

The CPU 14 may be provided with a further input representative of the number of cells in a particular battery under charge. Two thumbwheel switches 20 permit setting of any decimal number up to 99. The switches incorporate a binary coded decimal converter connected through an octal tristate buffer 21 to the CPU.

With this further input to the CPU the stored programme in the EPROM may also provide for the print out to include a column giving the average volts per cell of the cattery under charge.

Claims

1. A physical variable monitor comprising: means for receiving consecutive digital signals representative of the value of a physical variable at predetermined time intervals; memory means for temporary storage of said digital signals: processor means for calculating the mean of a predetermined number of consecutive said temporarily stored signals and comparing said mean with a previously calculated said mean to determine whether said calculated mean differs from said previously calculated mean to more than a predetermined extent; clock means; and means for storing said calculated means signal when it so differs and for simultaneously storing a clock signal.

2. A monitor according to claim 1 including an analog to digital converter for receiving analog input signals from a physical variable sensor and converting the analog input signal into said consecutive digital signals.

3. A monitor according to claim 1 or claim 2 wherein the comparing means is adapted to permit adjustment of said predetermined extent of difference between successively calculated said mean signals.

4. A monitor according to any one of claims 1 to 3 including a printer adapted to print out a stored calculated mean signal and its associated clock signal.

5. A monitor according to claim 4 wherein said printer is adapted for selective connection to and disconnection from said monitor.

6. A monitor according to any one of claims 1 to 5 including means to generate an alarm signal or a control signal or both when the digital input signal exceds a threshold or when the rate of change of the input signal value exceeds a preset rate or both.

7. A monitor according to any one of claims 1 to 6 wherein said processor means comprises a microprocessor and wherein said receiving means and said processor means each comprise parallel input/output port means compatible with said microprocessor.

8. A monitor according to any one of claims 1 to 7 adapted to serve as a battery charging monitor, said physical variable being battery voltage.

9. A battery charging monitor substantially as described herein with reference to the accompanying drawings.