JPS6117949A - Solid ph sensor - Google Patents

Abstract

PURPOSE:To make construction simple and manufacture easy and to make measurement with large output electric power by using electrodes consisting of different metals and detecting the electric current generated by bringing the two electrodes into contact with an aq. soln. to be measured in the form proportional to pH concn. CONSTITUTION:The electrode of the sensor is formed of the electrodes consisting of the different metals, for example, an Al electrode 1 and Zn electrode 2 and an insulator 3 for insulating both electrodes 1, 2. The current proportional to H<+> ion is generated together with a specified voltage in the circuit when the two electrodes 1, 2 are electrically coupled by bringing the liquid to be measured into contact with the electrodes 1, 2 to form a voltaic cell by the H<+> ion existing in the liquid. The output electric power in this case is read by a DC ammeter A and is measured. The electrode constitution is thus made simple and the manufacture is easy. The output electric power is increased and the measurement is made possible without using an amplifier circuit in some case.

Description

DETAILED DESCRIPTION OF THE INVENTION Conventionally, a glass electrode has been used in the sensor of a pH meter. However, since the glass electrode uses a glass thin film of about 0.025 mm, it is easily broken.

In addition, sensitivity and stability are easily affected by the glass composition used, making it difficult to manufacture (Currently, Corning's 5i0272, which has a composition of 2% Ca06 and Na2O2, is considered to be good). In addition, cleaning of the sensor part is required, and in particular, for industrial pH sensors, the cost of installing a cleaning machine is high, and 3.
Since it is a measurement of a high resistance of 0 to several 100 MΩ, it requires an amplifier circuit with a large input resistance, making it difficult to design two circuits.

Therefore, in recent years, research has been actively conducted to put 5olid 5tate pH sensors into practical use.

As an example of this, attempts have been made to put FET (field effect transistor) sensors into practical use using semiconductors, but semiconductors generally have the disadvantage of being easily damaged by temperature, so they have not been put into practical use to date. Sensors using semipermeable polymer membranes are also being developed, but the principle is the same as that of glass electrodes.

The pH sensor developed here is a power generation sensor that uses electrodes made of different metals, and is completely different from the conventional principle. The electrode structure is simple and therefore easy to manufacture, and the output current is large.

A major feature of this method is that in some cases, measurements can be made by simply connecting directly to a DC needle without using any amplifier circuit.

Figure 1 shows the electrode configuration of the sensor. (1) is the A1 electrode, (2) is the Zn electrode, and (3) is the insulator for insulating both electrodes.The prototype sensor was made of epoxy resin, acrylic (
PMMA) was used.

In the measurement method, when the liquid to be measured is brought into contact with both electrodes, the H ions present in the liquid form a Voltaic battery.
When the two electrodes are electrically coupled, a constant voltage and a current proportional to the H ions are generated in the circuit.

If the output voltage in this case is E, a quadratic equation is established.

E-1αRT-IJoy [H] ・・・・・・・(
1) α: Proportionality constant R: Gas constant T: Temperature, that is, -1oPU,H] An output voltage proportional to the temperature is obtained. This is read by a DC meter (4).

Figure 2 shows actual measurements of changes in current proportional to pH concentration using a prototype sensor.

In order to perform reproducible measurements for each measurement, it is necessary to clean the sensor head and keep the electrode surface clean at all times. For this purpose, it is currently cleaned by wiping with a cloth or using an ultrasonic cleaner.

[Brief explanation of drawings]

Figure 1 shows the configuration of the prototype solid-state sensor and detection method, with (1) the A1 electrode and (2) the Zn electrode. (3) is an electrical insulator, and here epoxy resin is used. A I) Check with the electric meter. FIG. 2 is a diagram showing the relationship between pH and current value actually measured by the above-mentioned sensor. The current was directly read using an ordinary digital DC meter.

Claims (1)

[Claims] A dissimilar metal such as Zn, Al, Cu, or stainless steel is used as an electrode, and the current generated by contacting the aqueous solution to be measured between the two electrodes is electrically captured in a form proportional to the pH concentration. pH sensor.