Digital point level switch method and apparatus
US4140908A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Aug 4, 1977 |
| Grant date | Feb 20, 1979 |
| Priority date | — |
| Expiry date | Aug 4, 1997 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01F23/2885
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
In a switching circuit for controlling the level of material in a container, a first counter accumulates pulses generated at a rate inversely related to the level of the material up to a first predetermined total. A second counter accumulates clock pulses up to a second predetermined total representing a fixed counting interval. The counters are connected in a race circuit wherein the one to reach its predetermined total first resets both counters and controls the race circuitry. The first counter sets a control circuit to indicate a low level condition or to activate an alarm, and the second counter resets the control circuit to indicate a high level condition. After the control circuit has been set by the first counter, the race circuit is responsive to a third predetermined total of the first counter, less than the first predetermined total, representing, for example, a level to which a container is to be filled. The first and third predetermined totals provide a hysteresis effect to prevent the switching circuit from "hunting" around the level at which material is to be added or an alarm condition shown.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.