RU1810804C - Device for multichannel measurement of emf of ion-selective electrodes - Google Patents

Abstract

Usage: electrochemical analysis of liquid media. SUMMARY OF THE INVENTION: the device comprises a registration, a high-resistance repeater, a tuned capacitor, switching elements, an electrometric switch, each ion-selective electrode is connected by a shielded cable through a switching element to the input of a high-resistance repeater and through an electromechanical switch with a tuning capacitor. A cable shielding braid is connected through a switching element to a common bus or high impedance repeater output and recorder input. 2 ill.

Description

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The invention relates to ionometry, in particular to a productive multicomponent and multi-point analysis of liquid media using ion-selective electrodes (ISE).

The purpose of the invention is to increase the speed of the device, increase the accuracy of ionometric analysis, simplify manufacturing technology and reduce the cost of the construction of the trimming capacitor by eliminating the influence of the insulation resistance of the trimming capacitor on the measured EMF.

This goal is achieved by the fact that in the circuit of the device for multichannel measurement of EMF, containing channel switching elements and switching elements with a changeover contact, changing the screening nature of ISE, VP, tuning capacitor connected in parallel with the input of the VP, RU, the input connected to the output of the VP, switching element connecting the VP input to the common bus of the device, as well as the actual electrode systems, in which the conclusions of the reference electrodes are connected to the common bus of the device, the conclusions of the ISE through the corresponding the connecting contacts of the channel switching elements are connected to the input of the VP, and the terminals of the screen braids of the ISE cables are connected to the common terminals of the change-over contacts of the corresponding switching elements, the terminals of the normally closed contacts are connected to the common bus of the device, and the terminals of the normally open contacts are connected to the output of the VP, an electrometric switching element is introduced providing shutdown of the tuning capacitor immediately after connecting the corresponding electrode system to the input of the VP.

Such a disconnection of the tuning capacitor from the input of the VP prevents distortion of the measured EMF

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of the electrode system due to the influence of heat currents through the isolation of the tuning capacitor, i.e. It allows one to increase the accuracy of ionometric analysis, simplify manufacturing technology and reduce the cost of the tuning capacitor.

1 schematically shows the proposed device. figure 2 - circuit electrometric contact.

The device (n measuring channels) contains the actual electrode systems 1.1,1.2, .. ,, etc. in which the conclusions of the comparison electrodes 2.1, 2.2, ..., 2.p are connected to the common bus of the device, and the conclusions of the ISE 3.1, 3.2, .... Zp, the common bus of the device and one output of the tuning capacitor 4 through the contacts of the switching elements 5.1, 5.2, ..., 5.p, 5p + 1, 5.P + 2 are connected to the input of the power supply with the output connected to the switchgear 7. The second output of the tuning capacitor 4 is connected to the common bus of the device. The common terminals of the changeover contacts of the switching elements 8.1, 8.2, ..., 8.p are connected to the conclusions of the ISE screen braids of the corresponding electrode systems 1.1, 1.2,.,., 1, p, the normally closed conclusions of their changeover contacts are connected to the common bus of the device, and normally closed conclusions of contacts - to the input of VP 6,

The device operates as follows. In the initial position of the contacts of the switching elements, the electrode systems 1.1, 1.2, .. ,, mi and magnitude of the EMF of the electrode system.

Previously, before conducting a cycle of multichannel EMF measurements for each electrode system, similarly to the prototype, the capacitance of the ISE cable and the total value of the capacitance of the tuning capacitor 4 and the input capacitance are equalized. VP 6 by adjusting the value of the capacitance of the trimmer capacitor 4 connected to the input of the VP.

After the adjustment, the remaining operations of the measurement cycle are carried out:

- simultaneous connection of the device’s zero bus and the tuning capacitor 4 to the input of the VP 6 through the contacts of the switching elements 5.p + 1 and 5.P + 2, respectively, and for each electrode system the required value of the capacitance 4 set as a result of adjustment is set;

- Disconnecting the contacts of the switching element b.p + 1;

- simultaneous connection of the electrode system through the corresponding contacts of the switching element 5.I to the input of VP 6 and the conclusions of the screen braid 9.I of the corresponding ISE to the input of VP 6;

- disconnecting the tuning capacitor 4 from the input of the VP 6 by the contact of the electrometric switching element 5.P + 2, produced immediately after the connection of the corresponding electrode system to the input of V P 6;

- direct measurement of EMF (taking readings from RU 7);

- shutdown of the electrode system

5- bringing the contacts of the switching elements 5.I and 8.I to the initial state.

Disconnecting the electrode system from which the EMF was measured can be combined with the operation of connecting the zero bus and the tuning capacitor 4 with the required capacitance value for the next electrode system to the VPB input, and disconnecting the contacts of the switching element 5.P + 1

5 - with connecting the electrode system to the input. VP 6.

The inventive device was implemented in the layout of the technical design of a program-controlled switch module

0 electrode potentials. In the device that implements the tuning capacitor, a set of serial small-sized capacitors of the type KT-1, KT-2 and KTI of the required ratings is used. The electrometric contact connecting the intermittent capacitor to the input of VP 6 is made on the basis of the serial magnetically controlled sealed contact KEM-3 according to the circuit shown in Fig. 2. Leakage currents in this

In the case 0, they do not exceed A, which effectively disconnects the tuning capacitor from the VP input and practically does not affect the measurement error of the EMF from electrode systems with ISE. It is also possible to use

5 electrometric relay type RV-3, RV-4. The time interval between connecting the electrode system and disconnecting the tuning capacitor was selected on the order of 5 ms, which is obviously longer than the time spent for scanning the electrometric contact (the maximum Hotk for KEM-3 is 3 ms) and the time for establishing the potential at the output of the VP based on the differential operational amplifier

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Claims (1)

SUMMARY OF THE INVENTION A device for multichannel measurement of the EMF of ion-selective electrodes, comprising a recording device, a tuning capacitor, a high-feed a repeater, channel switching elements and switching elements with a changeover contact in each channel, wherein the ion-selective electrode of each channel is connected by a shielded cable through the switching element to the input of a high-resistance repeater, the shielding braid of the cable of each channel is connected through the switching element with a change-over code dp G Fie. 1 Go out W K trimmer    J capacitor fig contact with a common bus or the input of the recorder and the output of the high-resistance repeater, characterized in that, in order to improve performance, the device further comprises an electrometric switching element connected between the trimmer capacitor and the input of the high-resistance repeater. To trimming capacitor