JPS58169044A - Constant temperature type pirani vacuum gauge - Google Patents

Abstract

PURPOSE:To indicate atmospheric pressure in inverse proportion when a Pirani gauging resistance etc. is abnormal, by a method wherein a bridge circuit comprising a Pirani gauging resistance is combined with an offset amplifier and a feedback circuit with a by-pass feeder. CONSTITUTION:Heat release from a Pirani gauging resistance Rs depends on atmosphere to be measured. It is less in low pressure, and increases as atmosphere to be measured approaches to atmospheric pressure. Voltage VE corresponding to heat release electric power Ps is max. in atmospheric pressure, and is min. in vacuum, while a gauging output Vout is 0V in atmospheric pressure, and is full-scale in vacuum as it is an inverse output of VE. When some abnormality occurs in the circuit, or the Pirani gauging resistance Rs is short-circuitted or disconnected, the gauging output Vout is shown as 0V. Further, the resistance Rs is opened, the gauging output Vout is also shown as 0V.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vacuum gauge, and relates to a constant temperature Villany vacuum needle.

This food vacuum needle has three resistances (R1*R1*Rs) with a metal oil line-shaped Villany measuring resistance (this is called R8).
When trying to keep the temperature of R8 constant by supplying power to this circuit, the power supply is supplied in response to the change in the amount of heat dissipated from R8 depending on the degree of vacuum. This is a book that measures the degree of vacuum by changing the current. It is called a constant temperature type because the temperature and therefore the resistance value of R6 are kept constant by increasing or decreasing the supplied current.

Conventionally, such a circuit has been incorporated into a WienBrie oscillation circuit, and G11l! which determines the amplitude. R8 is used as the element.

However, this vacuum gauge has problems such as poor temperature characteristics and is affected by the gain of the amplifier used in the oscillation circuit, and is also important in that the method of indicating the measured value is the same as in a vacuum state when an abnormality occurs. Inconveniently, instructing as low pressure at the time of this abnormality causes an inconvenient situation when controlling the operation of the vacuum device based on the output of the vacuum gauge. For example, if the Villany measuring resistor is de-energized and a low pressure indication is given, the vacuum cover may continue processing operations and the operating sequence continues. This is equivalent to performing a processing operation without measuring the degree of vacuum, resulting in an inconvenient situation.

The present invention has been made in view of the above-mentioned points, and is capable of reversing the polarity of the vacuum degree measurement signal from the Villany measuring resistor before taking it out, and also ensuring that even if the Villany measuring resistor becomes short-circuited, it will be in an open state. It consists of a constant temperature Villany vacuum needle that indicates the atmospheric pressure state even when the pressure is on.

An embodiment of the present invention will be described below with reference to the accompanying drawings.

In the figure, R is the Villany measurement resistance, and the resistance R1+
R1e R1 together with R1 constitutes a circuit, and Villany measurement resistor R8 is connected to the cable and noise filter IP.
is connected to other resistors in the circuit via This bridge circuit is connected to a resistor R from the feedback circuit FB.
・The outputs of the output points M and B are each connected to a resistor R4.

R, to the amplifier engineer 01. Here, the resistor R4 + ``1'' is appropriately selected to apply an offset with the input bias current of the amplifier 101 to prevent oscillations that may occur during low pressure measurement. When it begins to flow, R4<< Rm
, when flowing, R4>>R1. This amplifier engineer
1 output terminal resistance R@+R? The interconnection point between resistors R and R7 is connected to the power supply + terminal through a reverse current blocking diode DI, and the feed circuit is connected to the power supply + terminal via It is connected to the pace of transistor Q of B. transistor Q
A bypass resistor RB is connected in parallel to the collector emitter and resistor of the circuit, and when the output of the resistor RB is applied to the circuit through the resistor Ro as described above, the resistor K and the resistor R- are connected in parallel. It is applied to the inverting input terminal of the polarity inverting amplifier through the inverting input terminal. In this amplifier 03, the inverting input terminal is connected to the resistor R through the resistor R.
111 and a variable voltage source consisting of a variable resistor VR, while the non-inverting input terminal is grounded via a resistor Itu. Between the input and output terminals of the amplifier is connected a feed pad element consisting of a parallel circuit of a resistor R1t, a capacitor O, and a diode p3 with a resistor Rts connected in series, and a parallel circuit and a resistor R1m. The measurement output is taken out from the interconnection point.

The operation of Jin's circuit is as follows.

The Villany measurement resistor R8 radiates heat depending on the atmosphere to be measured, and the amount of heat radiated is small at low pressure and high vacuum, and increases as the pressure approaches atmospheric pressure. The amount of heat radiation is expressed as electric power P8.

P roX R8 , and when the bridge is balanced, the power ξ and the voltage V yo of the F transistor Q are.

v, -xFtl 1c: Constant of proportionality A voltage vR corresponding to the heat dissipation power P8 is obtained.

This voltage V is the maximum when the atmosphere to be measured is atmospheric pressure,
It is minimum in vacuum, but the measured output Vout is the inverse of that, so it is Ov at atmospheric pressure.

Full scale in vacuum.

The value of this measurement output Tout is determined by the voltage V and the resistance R1
The current flowing through the resistor R due to the current flow and the variable voltage source voltage v8
Since the sum of the current IP and the current flowing through the resistor R1m in the 74-doped silicon element flows through the resistor R1m.

Vout--RHg (IRI Juuko R-). Therefore, if we take IR@ and choose the value of R13 appropriately, VOut-
A predetermined value, for example 10V, can be set at O1 vacuum.

Next, the operation when a circuit abnormality occurs will be described. The circuit abnormality mainly includes a short circuit or disconnection of the Villany measuring resistor R8. This is because this resistor R8 is used by exposing an extremely thin wire to the atmosphere to be measured.

First, when the resistor RB is short-circuited, since the voltage at the point M of the bridge circuit is O, the maximum value of v and Fi, and hence the measured output Vout-07. The diode D3 is provided to clamp the output at this time so that it does not become too negative.

Further, when the resistor R8 is open, the transistor q is turned off when the voltage at the point M>the voltage at the point B of the bridge circuit. In this case, power is supplied to the pre-drop circuit via resistors RB and R. Here, the resistance value of resistor RB is the resistance R of the circuit.
Since it is selected to be considerably smaller than that of * + "*, the measured output Vout becomes OV at the maximum value of the voltage vBFi.

That is, if the Pirani measurement resistor R8 is short-circuited or disconnected, the measurement output VOut becomes OV, the same as when measuring atmospheric pressure.

This means that when controlling the operation of vacuum equipment using the measurement output Vout, the operation sequence can be stopped.

As described above, the present invention includes a bridge including a Villany measuring resistor,
By combining the circuit with a feed circuit with an offset amplifier and a bypass feed path, a measurement signal proportional to the atmospheric pressure was obtained, and this was output via a salary inversion circuit. It is possible to provide a vacuum gauge that is inversely proportional to atmospheric pressure and that indicates atmospheric pressure when there is an abnormality in the Villany measurement resistance or power supply.

In addition, the present invention #'i has the same flow side flow operation form.
– by connecting multiple circuits to a current source.

Multiple points can be measured simultaneously without phase-4 interference,
Moreover, it can be configured compactly as a pressure measurement circuit for control.

[Brief explanation of drawings]

The figure is a circuit diagram of an embodiment of the present invention. R8...Pirani measurement resistance, RB...Bypass resistance, R1~R11"' resistance, VR-...Variable resistance, I
ol, IOs...amplifier, Q...transistor, D
I! DI...diode, MP...noise filter, IFB...feedback circuit. Applicant's agent Kiyoshi Inomata Procedural amendment 1.・J [Indication of 1982 Patent Application No. 52557 2, Name of the invention Constant temperature Villany vacuum gauge 3, Person making the amendment Relationship to the case Patent applicant 7, Full text of the specification subject to the amendment and drawings

Claims (1)

[Scope of Claims] 1. A BRI circuit that is composed of a Villany measuring resistor and a fixed resistor and produces a small output when measuring vacuum and a large output when measuring atmospheric pressure, and an amplifier that amplifies the output of this BRI circuit; A feed path circuit that supplies power to the bridge circuit according to the output of the amplifier, a bias resistor that is connected in parallel to the feed path circuit and feeds power to the bridge circuit, and a polarity polarity for the output of the amplifier. Nine constant temperature type Pirani vacuum needles equipped with an inverted output circuit. 41. In the vacuum gauge according to claim 7. A constant temperature Pirani vacuum needle that applies an offset to the input terminal of a Tsumugi amplifier. 7.411 Range of Permissible Requests A constant temperature type Villany vacuum needle in the vacuum gauge according to item 1 or 2, wherein the Villany measuring resistor is connected to a power distribution circuit through a noise filter.