# US 4,398,188 A · Ground circuit voltage detector > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,398,188 A - Document ID: US4398188A - Status: Granted - Kind: A - Application number: 06/309,443 - Filed: 1981-10-07 - Granted: 1983-08-09 - Earliest claimed: 1981-10-07 - Inventors: Donn L. Feigal; Ronald R. Feigal - Web page: https://patentgrep.com/patent/US4398188A ## CPC - H02H 3/14: responsive to occurrence of voltage on parts normally at earth potential {(monitoring earth connection H02H5/105)} - G01R 19/16576: {comparing DC or AC voltage with one threshold (G01R19/16514, G01R19/16519, G01R19/16528, G01R19/16533 and G01R19/1659 take precedence)} - G01R 27/18: Measuring resistance to earth {, i.e. line to ground} - H02H: EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS (indicating or signalling undesired working conditions G01R, e.g. G01R31/00, G08B; locating faults along lines G01R31/08; emergency protective devices H01H) - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) ## Abstract A ground circuit voltage detector for monitoring stray ground voltages occurring in dairy equipment to provide both an instantaneous warning indication and a sustained alarm indication. The voltage detector is connected between the equipment to be monitored at a sensing input and a separate ground. The sensed voltage is filtered and applied to a first comparator through an averaging circuit. If the average ground voltage exceeds the threshold level of the first comparator, a warning indication is provided which is proportional in strength to the sensed ground voltage. The first comparator is connected in series with a second comparator through an integrator. If the threshold level of the second comparator is exceeded, a sustained alarm indication is provided. A test circuit applies a voltage to the detector input to ensure the detector is operating properly. ## Claims ### Claim 1 A voltage detector for monitoring the ground voltage developed in equipment and connected between the equipment and a separate ground connection, comprising: means for sensing the voltage developed in the equipment; means for comprising the sensed voltage to a first reference voltage and for providing an output proportional to the sensed voltage each time the sensed voltage exceeds the first reference voltage; means for providing a warning indication each time the sensed voltage exceeds the first reference voltage; means for comparing the output of the first comparing means to a second reference voltage; and means for providing a sustained alarm indication if the output of the first comparing means exceeds the second reference voltage. ### Claim 2 (depends on 1) The voltage detector of claim 1 wherein the warning indication means provides a warning indication proportional in strength to the sensed voltage. ### Claim 3 (depends on 1) The voltage detector of claim 1 wherein the alarm indication means further includes a reset means, the sustained alarm indication remaining on until reset by the reset means. ### Claim 4 (depends on 1) The voltage detector of claim 1 wherein the sensing means further includes means for averaging the voltage sensed, the first comparing means comparing the average sensed voltage to the first reference voltage. ### Claim 5 (depends on 1) The voltage detector of claim 1 further including means for integrating the output of the first comparing means, the second comparing means comparing the integrated output of the first comparing means to the second reference voltage. ### Claim 6 (depends on 1) The voltage detector of claim 1 wherein the separate ground connection is provided by an earth connection spaced a distance from the earth connection of the equipment to be monitored. ### Claim 7 (depends on 1) The voltage detector of claim 1 wherein the sensing means further includes an input terminal for connection with the equipment to be monitored and further including test means connected to the input terminal and actuable to apply an alternating voltage to the sensing means for determining whether the voltage detector is operating properly. ### Claim 8 (depends on 7) The voltage detector of claim 7 wherein the test means is actuable prior to the connection of the input terminal to the equipment for providing both the warning indication and the alarm indication if the voltage detector is operating properly. ### Claim 9 (depends on 7) The voltage detector of claim 7 wherein the test means is actuable to provide both the warning indication and the alarm indication if there is a faulty connection between the voltage detector and the separate ground. ### Claim 10 A voltage detector for monitoring the ground voltage developed in equipment, comprising: means for sensing the average ground voltage developed in the equipment; a first comparator for comparing the sensed ground voltage to a first reference and for providing an output signal if the sensed ground voltage exceeds the first reference; means for providing an instantaneous warning indication in response to the output signal of the first comparator; means for integrating the output signal of the first comparator; a second comparator for comparing the integrated output of the first comparator to a second reference voltage; and means for providing an alarm indication if the integrated output of the first comparator exceeds the second reference signal. ### Claim 11 (depends on 17) The voltage detector of claim 17 wherein the second comparator further includes latching means to maintain the alarm indication if the second reference voltage is exceeded. ### Claim 12 (depends on 11) The voltage detector of claim 11 further including means for resetting the second comparator to terminate the alarm indication. ### Claim 13 (depends on 10) The voltage detector of claim 10 wherein the instantaneous warning indication is proportional in strength to the sensed ground voltage.