JPH03235030A - Digital quartz vacuum gauge - Google Patents

Abstract

PURPOSE:To instantaneously and correctly output and display the calibrated pressure of a plurality of gases by storing the pressure data of a plurality of gases into a ROM and selecting the same by a bit switch. CONSTITUTION:A resonance current is converted to a voltage signal by an I/V converter 3 and amplified by an amplifier circuit 4 and then, rectified to a direct current voltage signal by a rectifier circuit 5 at a next stage. The voltage signal is converted by an inverter circuit 6 and a buffer circuit 7 which can adjust the bias voltage so that 10V is output at the atmospheric pressure and 0V is output at high vacuum. Thereafter, an analog voltage signal output from the buffer circuit is A/D converted at 8 and input to an address of a ROM 9. The pressure data output from the ROM 9 is, via a decoder driver 11, output and displayed by a digital display device 12.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to a vacuum pressure measuring device, and more particularly to a quartz vacuum gauge that utilizes the fact that the electrical characteristics of a quartz crystal resonator change depending on gas pressure.

[Summary of the invention]

The present invention converts an analog voltage signal into a digital signal,
ROM that stores pressure data for various gases in advance
By converting digital signals into pressure signals,
The present invention provides a digital display type quartz vacuum gauge that obtains pressure display outputs with sensitivities calibrated for a plurality of gases.

[Prior Art] Since it has been known that the resonant impedance of a crystal resonator shows dependence on the surrounding pressure over a wide range, this phenomenon has been utilized to reduce pressures from atmospheric pressure to 1 O-3 Torr. Crystal vacuum gauges capable of continuous measurement with one sensor have been proposed, for example, as disclosed in JP-A-60-57231-R Gas Pressure Gauge and JP-A-61-10735-R Gas Pressure Gauge. A block diagram of the measurement circuit is shown in FIG. The oscillation circuit 1 causes the crystal resonator 2 to constantly vibrate in a resonant state, and the resonant current is converted into a voltage signal by the IV converter 3.

The crystal oscillator 2 serves as a pressure measuring element that comes into contact with the atmosphere to be measured. The voltage signal is amplified by an amplifier circuit 4 and then passed through a rectifier circuit 5 to output a DC voltage. This DC voltage signal is transmitted by the meter drive circuit 13.
By converting to full scale at atmospheric pressure and zero at high vacuum, and driving the meter display 14,
Display pressure.

[Problem that the invention seeks to solve]

Figure 3 is a diagram showing the relationship between the output voltage and pressure depending on the type of gas of the crystal oscillator.As is clear from Figure 0, it is understood that the pressure sensitivity of the crystal oscillator varies considerably depending on the type of gas6. Correct pressure measurements can be made by displaying the scale of the meter according to the type of gas being measured, but having too many scales makes it difficult to read, so it is usually
The meter display 14 has pressure characteristics in nitrogen gas engraved on a scale plate. Therefore, when measuring the pressure of a gas other than nitrogen gas, the exact pressure cannot be known unless it is converted by using a sensitivity calibration table, which is very troublesome. especially,
The sensitivity of hydrogen gas is several tenths of that near atmospheric pressure, so it indicates a pressure lower than the actual pressure, and there was a risk of an explosion if unnoticed even if the pressure was abnormally high.

[Means for Solving the Problems] The present invention was made to solve the problems of the prior art, and it converts an analog voltage signal into A/D and converts the address of a non-volatile memory (hereinafter referred to as ROM). Enter. Pressure data is written in the address of the ROM, and the data output is output and displayed on a digital display via a decoder driver.

[Function 1] The pressure characteristic data of the output voltage according to the type of gas shown in Fig. 3 is written in the ROM, and the pressure data whose sensitivity has been calibrated using a bit switch etc. is output according to the gas to be measured, thereby controlling the gas pressure. The output can be displayed accurately.

[Example〕 Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a circuit block diagram of a crystal vacuum gauge according to the present invention. A zero oscillation circuit 1 drives a crystal resonator 2 at a constant voltage in a constant resonance state, and is a self-excited oscillation circuit or
By means such as a phase-locked loop (PLL circuit). The crystal oscillator 2 serves as a pressure measuring element that comes into contact with the atmosphere to be measured. The resonant resistance of the crystal resonator 2 is measured by measuring the resonant current. The resonant current is converted into a voltage signal by an IV converter 3, AC amplified by an amplifier circuit 4, and then rectified into a DC voltage signal by a rectifier circuit 5 at the next stage. As shown in Figure 4, this DC voltage signal has a pressure characteristic of the resonant current of the crystal resonator, and as the pressure of the surrounding gas decreases, the resonant current increases. I was supposed to show
It's unnatural. Therefore, by using the impark circuit 6 and the buffer circuit 7 which can adjust the bias voltage,
It is converted to output V, and Ov when in high vacuum. The analog voltage signal output from the buffer circuit is converted into a digital signal by the A/D converter 8 and input to the address of the ROM 9 . Since the ROM 9 stores data on the output voltage and pressure characteristics shown in FIG. 3, the pressure data is stored in advance at the address corresponding to the analog voltage signal. ROM9
The pressure data outputted from the decoder driver 11 is output and displayed on the digital display device 12. FIG. 5 is a detailed block diagram of the circuit from the A/D converter to the digital display device.

The A/D converter 8 is composed of 12 bits, and its output is RO
Connect to address inputs of M9A and 9B. ROM9A
ROM 9B stores pressure mantissa data, and ROM 9B stores pressure exponent data. - For example, if a ROM with a word x 8 bit configuration is used in 32, nitrogen gas data will be stored in addresses 0 to 4095, argon gas data will be stored in addresses 4096 to 8191, and hydrogen gas data will be stored in addresses 8192 to 12287. Up to eight types of gas pressure calibration data can be written. Therefore, calibrated pressure data can be read out by selecting gas pressure data using a bit switch IO or the like depending on the type of gas to be measured. The 8-bit data output of the ROM 9A outputs the pressure mantissa value to the 2-digit digital display device 12 through the decoder driver IIA. Similarly, the pressure index unit receives the address signal from the A/D converter 8, and the ROM 8B outputs pressure index data, which can be output to the digital display device 12 via the decoder driver IIB.

[Effect of the invention 1 According to the present invention, in a crystal vacuum gauge that utilizes the fact that the resonance characteristics of a crystal resonator depend on gas pressure, an A/D converter that converts an analog voltage signal into a digital signal, and a digital signal are provided. It is composed of a ROM that converts the pressure into a pressure signal, a decoder driver, and a digital display device. By storing various gas pressure data in the ROM and selecting it with a bit switch, it is possible to display pressures with calibrated sensitivity for multiple gases. It can obtain output instantly and accurately, and has high practical value.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram of a quartz vacuum gauge according to the present invention. FIG. 2 is a conventional circuit block diagram. Figure 3 is an analog output voltage-pressure characteristic diagram of various gases of the crystal resonator,
FIG. 4 is a pressure characteristic diagram of the resonance current and resonance resistance of the crystal resonator. FIG. 5 is a detailed circuit block diagram according to the present invention. Oscillation circuit Crystal resonator I/V converter Amplifier circuit Rectifier circuit A/D converter Non-volatile memory (ROM) Bit switch Decoder driver Digital display device and above Figure 1 Conventional thick vacuum needle circuit 70.27 Figure 2 figure

Claims (1)

[Claims] A crystal vacuum gauge that utilizes the fact that the resonance characteristics of a crystal resonator depend on gas pressure includes at least an A/D converter that converts an analog pressure signal into a digital signal, a nonvolatile memory that stores pressure data, and a decoder. A digital display type quartz vacuum gauge comprising a driver and a digital display device and storing various gas pressure data in the nonvolatile memory to obtain pressure display outputs with sensitivities calibrated for a plurality of gases.