Patent GB-1196818-A (GB)
Title: Measuring Position Change-Over Switch.
IPC: G08C15/06
Filed: 1968-08-16
Abstract: 1,196,818. Measuring physical variables electrically. BARMAG BARMER MASCHINENFABRIK A.G. Aug.16, 1968 [Aug.18, 1967], No. 39318/68. Heading G1N. In an arrangement for connecting a number of measuring devices A, B, C, D.....Y, Z sequentially to a single indicator unit 1-5 by relays a, b, c, d. . .y, z controlled by a single timing pulse generator , the relays are divided into two groups a, c,...y and b, d...z which are supplied by overlapping pulses from the pulse generator and each relay a, b, c &c. has in its supply line a make contact e.g. z3, a3, b3 etc operable by a preceeding relay e.g. z, a, in the other group in the measuring cycle and a break contact, e.g. y4, z4, a4 etc, operable by a preceeding relay e.g. y, z, a in the same group, the sequence being interrupted if a deviation in the prescribed tolerance range of measurement occurs. As described, for measuring the temperature using thermocouples at a plurality of points, the thermocouples A, B, C &c. are connected sequentially via relay operated contacts a1, b1, c1 to a meter 1-5, the groups of operating relays being connected one group to line 13 and the other to line 14; lines 13, 14 being connected, via relay controlled contacts 17, 18 to D.C. supply line 12, and to supply line 11. Timing pulse generator. - The generator comprises essentially a realy 27 and relays 22, 31, connected across D.C. supply lines 11, 12, which latter relays operate after a preset time which determines the duration of each measurement. Initially when the circuit is switched on, relay 22 is energized closing a contact 26 after a preset time delay, to close the circuit of relay 27. Energization of the relay 27 causes a contact 21 to be opened to de-energize relay 22 and open contact 26, the relay 27 being held on by closing of contact 29. Additionally contact 23 is opened and contact 28 closed to de-energize and energize relays 15, 16 respectively to disconnect line 13 from the D.C. supply after a brief time delay and to connect line 14 to the supply. The duration of energization of relay 27 is determined by the energization of relay 31, by closure of contact 30 by the relay 27, which, after the set time delay, opens contact 32 to disconnect the relay 27 from the supply. Relay 16 is consequently de-energized to disconnect line 14 from the supply after a brief time delay and the relay 15 is energized to connect line 13 to the supply. The duration of de-energization of the relay 27 is determined by the energization of the relay 22, by closure of contact 21 by de-energization of the relay 27 which, after a preset time delay closes contact 26 causing relay 27 to be re-energized. Switching cycle.- Initially when the circuit is switched on a relay 24 is energized to close contact 25 and connect relay a across the supply lines 13, 11, line 13 being connected at this time to line 12. Energization of relay a causes contact a1 to close to connect thermocouple A to the indicator 1-5, causes contact a2 to close to make the relay a self holding, closes contact a3 to prepare relay b for energization when line 14 is connected to line 12, and opens contact a4 to prevent relay c from being energized. At the end of the measurement time when relay 27 is energized, both lines 13, 14 are momentarily connected to the D.C. supply so that relay b is energized via still-closed contact a3 and becomes self holding by closure of contact b2 when relay a is de-energized. The relay b is provided with the same contacts as relay a so that the same proceedure is repeated as before and for all the other relays in sequence, the relay a being again energized via momentarily closed contact z3 of relay z when the relay 27 is deenergized after the measurement of the voltage of thermocouple Z. Measurement deviation.- If the measured value lies outside the limits set by devices 3, 4 of the meter one of two switches 33, 39, is closed to energize audible and visible alarms 36, 35, or 44, 43 and energize relay 34 or 40 to change over contacts 37, 38 or 41, 42. In the period when relay 27 is energized this has the effect of maintaining the relay energized even when contact 32 is opened by energization of relay 31, and equally when relay 27 is de-energized, it is maintained in this state, until switch 45 is manually opened to de-energize relay 34 or 40. When the switch is again closed the cycle continues as before. The switching circuit may be used to monitor pressure, flow or pH at a plurality of points. The timing pulse generator may be replaced by mechanical components, e.g. cam discs driven by motors which actuate contacts 17, 18 e.g. through relays similar to 15, 16.