The Smith Meter Stack Monitor combines a proximity switch with a 200A Series Counter and is normally mounted on a Smith Meter Positive Displacement (PD) Meter. When product flows through the meter, the wheels of the counter rotate. The switch detects the rotation of a steel “target” molded into the first counter wheel and produces a switch closure at the rate of one pulse per revolution of that wheel. The stack monitor switch detects rotation of the first right-hand wheel.
The Smith Meter Stack Monitor is primarily used in LACT installations to transmit a pulse output to a customer-supplied timed reset. When the LACT system pump is running, the timer must receive a pulse within a predetermined period of time. When a pulse is not received within the allotted time (indicating a “no flow” situation or accessory malfunction), the pump is automatically shut down. Intervention by alerted authoritative personnel is then required to restore system operation.
The stack monitor can also be used in other applications requiring a low-resolution pulse transmitter to interface with remote instrumentation or with complementary equipment such as additive injection systems or sampler pacers. The number of pulses per unit of the 200A Series Counter is transmitted by the pickup switch located on the first wheel. For example, the stack monitor provides one pulse per barrel with the rotation of the first right-hand wheel of a Model 207A-B Horizontal Non-Reset Counter.