JPS6051062B2 - Two-wire process analyzer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a two-wire process analyzer equipped with electrodes as detection means.

Generally, the objects to be measured by this type of analyzer are often contaminated.

Therefore, it is necessary to prevent excessive scale from adhering to the electrodes. Conventionally, a cleaning device was installed separately from the analyzer to prevent scale buildup. However, this conventional configuration
A disadvantage is that a separate power supply and power line for the cleaning device must be provided. An object of the present invention is to realize a two-wire process analyzer that can perform electrode cleaning without separately providing a power source and power line for a cleaning device.

Hereinafter, the present invention will be explained in detail using the drawings. FIG. 1 is an electrical circuit diagram showing an embodiment of a two-wire process analyzer according to the present invention (here, pH measurement is taken as an example). In the figure, GE is a glass electrode, RE is a reference electrode, and the tips of these electrodes are immersed in the liquid to be measured. Q, is an output transistor connected in series with transmission lines 1, , 12, Rc is a resistor, Q. is a field effect transistor (hereinafter referred to as FET), and D, , D2 are zener diodes. The resistor Rc and the FET Q2 form a constant current circuit CC that passes a portion of the current flowing from the power source E on the receiving side through the load RL (receiving device such as a recorder) and the transmission line 1. The output of this constant current circuit CC is connected in series with Zener diodes D, D. The voltage is regulated by the power supply lines B, , B as the power supply voltage. is given to. BT and Rf are a rechargeable battery and a negative feedback resistor connected in series to a transistor Q, respectively. Al and N are operational amplifiers, the non-inverting input terminal of the operational amplifier Al is connected to the glass electrode GE, and its output terminal is connected to the operational amplifier A through a switch SW. is connected to the inverting input terminal of Further, a hold capacitor Co is connected between the inverting input terminal and the output terminal of the operational amplifier, and the output terminal is connected to the base terminal of the transistor Q. Also, Zener diode D. Line B kept at a potential of
3 and the output terminal of the operational amplifier Al, there is a temperature measuring resistor Rt for compensating the temperature coefficient of the electromotive force of the glass electrode GE, and a variable resistor for correcting variations and deterioration of the electromotive force of the glass electrode GE. A series circuit with the device Rv is connected. The divided voltage of the variable resistor Rv is applied to the inverting input terminal of the operational amplifier A1. The comparison electrode RE is directly connected to line B3, and the non-inverting input terminal of operational amplifier A1 is connected to line B3 via a filter capacitor C.
Rl and R2 are resistors, and are they power lines? and one end of the resistor Rf (
The voltage between the transmission line 12 and the transmission line 12 is divided and applied to the non-inverting input terminals of the operational amplifiers. The above-mentioned operational amplifier Al receives current supply from the power supply line Bl,8.
, A, etc. form a conversion amplification section Cv. Therefore, the drive current of this conversion amplification section Cv is supplied from the constant current circuit CC. WS is a cleaning device for cleaning the electrodes GE and RE, which is shown here as consisting of a brush BR and a motor M that rotates the brush BR. The drive current for this motor M is supplied from a rechargeable battery BT. CON is a control device that controls the cleaning device, and is composed of a relay (may be a semiconductor switch) RY placed in the drive current path to the motor M, and a timer circuit TM that opens and closes the relay RY at regular intervals. ing. The drive current for the timer circuit TM is supplied from power supply lines Bl and B2. This timer circuit TM also has a function of keeping the switch SW open while the motor M is rotating even if the relay RY is closed. The operation of this device will be explained.

First, a normal measurement time when the cleaning device WS is not operating will be described. The voltage EI generated between the glass electrode GE and the comparison electrode RE (corresponding to the pH value of the liquid to be measured) is the voltage generated by the operational amplifier A.
1 and resistors Bt and Rv, it is converted into a signal of an appropriate magnitude, and then sent to an operational amplifier A via a switch SW.
It is applied to the inverting input terminal of No.2. Therefore, operational amplifier A2
controls transistor Q1 so that the potential difference between its input terminals becomes small. Therefore, the output signal 10 corresponds to the voltage Ei, which is the transmission line 11.
,1. becomes the current flowing through. The magnitude of this output signal 10 is usually selected to be 4 to 20 rT1A DC (in the measurement range 0 to 100%). Note that during this measurement, the rechargeable battery is constantly charged with the current flowing through the transistor Q1. Next, when the cleaning operation begins after a certain period of time (for example, one hour) has elapsed, the timer circuit TM first opens the switch SW.

As a result, the operational amplifier A2 and the capacitor CO operate as a hold circuit, so that the output current 10 is kept at a constant value. Next, the timer circuit TM closes the relay RY, supplies the electric power stored in the rechargeable battery to the motor M, and cleans the glass electrode GE and the comparison electrode RE with the rotating brush BR. After cleaning for an appropriate time, the timer circuit TM opens the relay RY to stop the rotation of the motor M, and then closes the switch SW. As a result, the cleaning operation is completed and the normal measurement operation is resumed. Thereafter, cleaning is performed at regular intervals. As already mentioned, the output current 10 is generally a small current of 4 to 20 rT1A DC, but in this embodiment, a rechargeable battery BT is arranged and the power stored there is used to drive the cleaning device WS, so the output current 10 is a small current of 4 to 20 rT1A DC. A cleaning device WS that requires electric power can be driven. Note that in the above description, a constant current circuit is shown as a drive circuit that provides a drive current to the conversion amplification section, but it does not necessarily have to be a constant current circuit.

In addition, although a cleaning device using a brush is shown, the same applies to other types of cleaning device.Furthermore, if cleaning is performed slowly, it is not necessarily necessary to adopt a configuration that holds the output during cleaning operation. In addition, the control device can be configured manually so that a cleaning command can be issued from the outside when necessary.The drive current for this control device can also be taken from a rechargeable battery.In addition, the rechargeable battery can be connected to an output transistor. It may also be connected to the collector side of the zener diode D.
3 and transistor Q2 are added to the circuit in Figure 1 (a partial diagram is shown in Figure 2), the rechargeable battery B
The charging voltage of T can be increased to the voltage Vcc of transmission lines 11 and 12. As described above, according to the present invention, it is possible to realize a two-wire process analyzer that can perform electrode cleaning without separately providing a power source and power line for the cleaning device.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an electric circuit diagram showing one embodiment of a two-wire process analyzer according to the present invention, and FIG. 2 is an electric circuit diagram showing a part of another embodiment.

GE, RE... Electrode, Q1... Output transistor, Rf... Negative feedback resistor, Cv...
・Conversion amplifier, CC・・Constant current circuit (drive circuit), BT
...Rechargeable battery, WS...Cleaning device, CON...
····Control device.

Claims (1)

[Claims] 1 An electrode as a detection means, an output transistor connected in series to a two-wire transmission line, a negative feedback resistor connected in series to this output transistor, and a voltage corresponding to the output of the electrode to this negative feedback. a conversion amplification section that controls the output transistor so that the current flows through the resistance; a drive circuit that supplies part of the current flowing through the transmission line to the conversion amplification section; and a rechargeable battery connected in series with the output transistor; The cleaning device includes a cleaning device for cleaning the electrode, and a control device that controls start and stop of power supply to the cleaning device, and uses electric power stored in the rechargeable battery as driving power for the cleaning device. A two-wire process analyzer characterized by: