Open collector transistor (optical isolator) is also provided.Ī Reset input is provided to stop the pumps and reset the timers. A second input, which requires an isolated contact or This feature allows theĭR1920 to be wired in parallel across the switch contacts without regard to theĮxisting control system, permitting simple installation in existing systems.įor situations where the existing wiring prevents this circuit from being used, an When the DR1920 senses a low impedance, it begins its control function, regardless of any absence or presence of voltage across the switch contacts. That measures the impedance present between the switch contacts. The DR1920 is wired across the alarm switch contacts and uses a unique circuit In addition, if the primary control system fails, the normal voltages may not be present. This switch may have any of several voltages that are The DR1920 monitors the open or closed status of a switch contact that is already
The DR1920 also has provisions to alarm on a switch opening. Timer 2 is set by the user to lower the level ito the desired low level. Pump 2 is not started and Pump 1 will run until Timer 2 reaches its set time. If the High-High Alarm switch opens during the Timer 1 interval, Timer 2 is started when the High-High Alarm switch opens. High-High Alarm switch contact opens, Timer 2 is started and both pumps continue to run until Timer 2 reaches its set time. Pump 1 and Pump 2 will run until the High-High Alarm switch opens. When Timer 1 reaches its set time, and the High-High Alarm switch is still closed, Pump 2 is started. When the High-High Alarm switch in the tank or well closes, the DR1920 closes a relay that starts Pump 1 and starts an internal Timer 1. It prevent overflows in situations where the primary level control system fails. The DR1920 Back-Up Pump Control is a compact DIN rail mounted unit used to monitorĪ backup High-High Level Alarm in a tank or wet well and to start up to two pumps when the High-High Alarm switch closes. Wilkerson Instrument celebrates 32 years experience designing, manufacturing, distributing, and providing engineering help for the process control industries. Isolated 2 Wire Transmitter, Head or DIN Rail Mountįactory Ranged Input ± 16mV to ± 128 VDC, ± 0.01mA to ± 100mADC
Span ± 16mV to ± 256VDC, ± 0.8mA to ± 100mAįour Models, Combinations of 4/20mA and 0/10VDC Input and Output
The Isolator can measure the small voltage across the resistor even though it is floating 138VDC above the system circuit common. The resistor drops a small voltage proportional to the battery current.
DC VOLATGE GROUND ISOLATOR SERIES
Example – A small resistor in series with the + lead of a 138VDC battery and the – side of the battery is the “common” lead for the system. The Isolator breaks the common lead and the AC current can no longer flow.Ī common mode voltage is a voltage that is connected to the + and – inputs of a device. The voltage appears in series with the desired signal and creates “noise” on the desired signal. AC current flowing in the common lead drops a small AC voltage due to the wire resistance. Ground loops are created when the source of a signal and the driven instrument have their common inputs tied to the earth at each device or the common lead is used to carry AC current for some other device. Isolators are used to break ground loops and to measure signals with high common mode voltages. DC Isolators Provide galvanically isolated DC Output proportional to DC Input
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