JPS62169033A - Driving system of pressure sensor - Google Patents

Abstract

PURPOSE:To reduce the current consumption to that of one semiconductor pressure sensor, by connecting two semiconductor pressure sensors in parallel to accomplish a selective time division driving. CONSTITUTION:A semiconductor pressure sensor S1 has a piezo resistances ra, rb, rc and rd bridge connected and sensor outputs +V01 and -V01 are derived according to a pressure to be applied. A semiconductor pressure sensor S2 also the same type as the semiconductor pressure sensor S1. A timing signal generator Tc generates two timing signals p1 and p2 in which the duty ratio is below 1/2 with the phase shifted from each other so that when one is high the other will be low to apply the timing signal p1 to a constant current circuit SI1 and the timing signal p2 to a constant current circuit SI2. When a high signal is applied to the constant current circuit SI1 or the constant current circuit SI2 with a timing signal generator Tc, the corresponding constant current circuit is put into operation to run a driving current through a corresponding semiconductor pressure sensor. As viewed in time series, a driving current always flows through only one semiconductor pressure sensor.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a method for driving a pressure sensor such as a differential pressure transmitter that detects a differential pressure using two pressure sensors.

(B) Prior Art Generally, when two semiconductor pressure sensors (eg piezoresistive pressure sensors) with the same characteristics are driven, they are driven with a constant current or a constant voltage. As a connection method for these two semiconductor pressure sensors, a parallel connection is adopted because the circuit configuration is easy, and a drive current is passed through each semiconductor pressure sensor separately and independently.

(c) Problems to be solved by the invention In the two-wire differential pressure transmitter, the output signal is 4 to 20 m DC.
A is adopted, and the current consumption of the entire circuit is 4.
It needs to be less than mA (about 2.5 to 3.5 mA). On the other hand, when two semiconductor pressure sensors are used in the detection section of this type of differential pressure transmitter, when the semiconductor pressure sensors are driven in the conventional parallel connection described above, drive current flows to each semiconductor pressure sensor separately and simultaneously. The current consumption of the detection section becomes large. Therefore, there is a problem that there is no margin for current consumption in other circuits of the differential pressure transmitter, making circuit design difficult.

In view of the above, an object of the present invention is to provide a pressure sensor drive method that can reduce the current consumption of the pressure detection section.

(d) Means and operation for solving the problem The driving method of the pressure sensor of the present invention is to connect the first and second semiconductor pressure sensors (St, SZ) in parallel to the power supply (+VS), and A current is made to flow selectively and sequentially through the first and second semiconductor pressure sensors based on a time division signal outputted from the division signal generating means (Tc).

In this pressure sensor driving method, two semiconductor pressure sensors are time-divisionally driven, and when current flows to one, no current flows to the other. Therefore, even though the semiconductor pressure sensors are connected in parallel, the drive current is small.

(E) Examples The present invention will be explained in more detail with reference to Examples below.

FIG. 1 is a connection diagram of a pressure sensor drive circuit in which the present invention is implemented. In the same figure, semiconductor pressure sensor S,
constant current circuit 31. are connected in series, and a constant current circuit S12 is connected in series to the semiconductor pressure sensor S2, and these series circuits are connected in parallel to the power supplies +Vs and Com.

The semiconductor pressure sensor S is composed of piezoresistors ra, rb, r
c and rd are bridge-connected, and sensor outputs +Vo, -Vol are derived according to the applied pressure. The semiconductor pressure sensor S2 is also the same type of sensor as the semiconductor pressure sensor S1.

As shown in FIG. 2, the timing signal generator Tc generates two timing signals p1, which have a duty ratio of 1/2 or less and are out of phase with each other, so that when one is high, the other is low.
p2 and sends the timing signal p1 to the constant current circuit S1.
, the timing signal p2 is sent to the constant current circuit S1. In addition to

In this embodiment circuit, when a high signal is applied to the constant current circuit SII or the constant current circuit S2 by the timing signal generator TC, the constant current circuit operates and a drive current flows to the corresponding semiconductor pressure sensor. . Therefore, drive currents corresponding to the waveforms of the timing signals p1 and p2 shown in FIG. 2 flow through the semiconductor pressure sensors S1 and St. As a result, when viewed in chronological order, the drive current always flows through only one semiconductor pressure sensor.

FIG. 3 shows another embodiment of the invention.

In addition to the example circuit of FIG. 1, this example circuit includes a power supply +Vs and a constant current circuit SI1. Constant current circuit S between SIZ
li is provided, and a Zener diode Z is connected in parallel to the series circuit of the constant current circuit 312 and the semiconductor pressure sensor S2. This Zener diode Z provides current bypass and constant voltage to constant current circuit S1. and semiconductor pressure sensor S
1. It is provided to apply to each series circuit of constant current circuit SI2 and semiconductor pressure sensor S2.

In this example circuit, the duty ratio of the drive currents flowing through the semiconductor pressure sensor SI and the semiconductor pressure sensor S2 is set to 1.
72, there is no waste in the current flowing through the Zener diode Z, and it is possible to eliminate waste in current consumption.

In the above embodiments, the semiconductor pressure sensor is driven with a constant current, but the present invention is also applicable to a semiconductor pressure sensor driven with a constant voltage.

Further, in the above embodiments, a bridge circuit type semiconductor pressure sensor is taken as an example, but the pressure sensor used in the present invention is not limited to a bridge type.

Further, although the above embodiment circuit is assumed to be used for differential pressure detection, the present invention is of course not limited to differential pressure detection, and can be applied to cases in which two independent pressure sensors are driven in parallel. Ru.

(f) Effects of the Invention According to this invention, two semiconductor pressure sensors are connected in parallel and driven selectively in time division. The current is approximately the same as, or less than, that in the case of using one semiconductor pressure sensor, and the design is facilitated from the viewpoint of limiting the current value of other circuit sections.

[Brief explanation of drawings]

FIG. 1 is a circuit connection diagram of a pressure sensor drive circuit in which the present invention is implemented, FIG. 2 is a timing waveform diagram for explaining the operation of the drive circuit, and FIG. FIG. 2 is a circuit connection diagram of a drive circuit for a pressure pinion sensor according to an embodiment. S, ・S2: Semiconductor pressure sensor, Sl, -5ix ・Sr3: Constant current circuit, +V s
: Power supply, TC: Timing signal generator. Patent applicant: Shimadzu Corporation Agent
Patent Attorney Shigeru Nakamura Figure 1 Figure 2

Claims (1)

[Scope of Claims] (2) The first and second semiconductor pressure sensors are connected in parallel to a power source, and the first and second semiconductor pressure sensors are controlled by a time-sharing signal output from a time-sharing signal generating means. A pressure sensor drive method characterized in that a current selectively and sequentially flows through the pressure sensor. (2) The pressure sensor driving method according to claim 1, wherein the power source includes a constant current circuit, and power is supplied to each of the semiconductor pressure sensors through the constant current circuit. (3) The time-division signals outputted from the time-division signal generation means are intermittent, have opposite phases, and have a duty ratio of 1.
Claim 1, wherein the first and second signals are equal to or less than /2.
A driving method for the pressure sensor according to item 1 or 2.