CM-800 HVAC / Municipal / Industrial Flow Meter
The Nusonics Model CM-800 Transit-time Ultrasonic Flow Meter can measure highly accurate flow rates in a wide range of fluids. Since the CM-800 utilizes transit time technology, it does not depend on the presence of particles to make an accurate measurement, like a Doppler flow meter. It will operate with high accuracy in a wide range of clean liquids. The flow meter can tolerate up to 2% by volume of particle or bubbles in the process stream without affecting the performance. Primary applications are in HVAC control systems, municipal water systems, oil/fuel oil and clear chemical streams. The CM-800 has a number of advanced features, including:
- Accurate measurement of flow +/- 1/2%-1% of reading
- No pressure drop, no moving parts
- Line sizes from 2″-200″
- Bi-directional flow measurement
- 4-20 mA and RS-232 outputs
- Optional on-board flow and total LCD Display
- Easy setup via hand-held configurator or PC
Flow Meter Components
Many of the components of a CM-800 are optional. This allows you to select a configuration which meets you application needs without paying for unwanted features. In its most economical form, an HVAC CM-800 with 4-20 mA output, (intended for interface with DCS), you can be assured of receiving the best reliability and accuracy available for the price.
The ultrasonic flow meter consists of two major elements; the transmitter electronics and a pair of transducers mounted on the pipe. The transmitter portion contains the circuitry which converts the transducer signals to an accurate flow measurement. These electronics are provided in a Nema 4X enclosure or an optional explosion proof Nema 7 enclosure. The transmitter assembly may also be equipped with a heater/thermostat, which permits operation of the flow meter in cold ambient conditions as low as -60° C (-76° F).
The ultrasonic transducers are provided in four different wetted configurations (HVAC, 1/2″, 1″ and 2″). All wetted transducers are mounted recessed from the pipe wall to avoid obstruction or pressure drop in the flow stream. Transducer pairs are mounted via an integral flange to weld bosses which are aligned on opposite sides of the pipe. The standard material of construction for 1″ and 2″ transducers is CPVC. Economical HVAC transducers, rated to 300 psig, have a removable design and can be easily changed without system shutdown. Optional metal transducers are available for higher temperature and special conditions. Generally, 1/2″ titanium transducers are utilized on pipes up to 6″, 1″ CPVC transducers from 8-24″, and 2″ CPVC transducers for all lines larger than 24″.
Most flow meters are provided with a factory calibrated flow-tube with the transducers tested, calibrated and ready for service. Flow tube installation options include ANSI or AWWA flanges, NPT threads, victaulic groove or weld-in-place. As an alternative, Mesa can provide flow meters in a kit form for installation of the transducers onto an existing pipe.
For pipes that do not allow easy welding of flow tube kit bosses, saddle mounted transducer assembly is available. This assembly is very useful for installing the sensor mounting hardware on concrete, cast iron, fiberglass and plastic pipes.
The CM-800 electronics are constructed on a single PC board for easy access and maintenance. The microprocessor accurately calculates the flow rate over a wide flow velocity range, from 0.3 to 50.0 ft/sec, automatically taking into account the Reynolds Number of the fluid to allow accurate measurement. The CM-800′s advanced microprocessor allows for dynamic zeroing of the flow meter. In addition, it has a range of other diagnostic tools to monitor both your flow process and the status of the flow meter system.
Hand-held CM-800 Configurator
The CM-800 is setup quickly and easily via either a hand-held configurator or an external PC. The hand-held configurator allows instantaneous reading of flow rate and totalization. Setup is as easy as stepping through a menu and filling in the blanks with data such as pipe diameter and fluid type. The hand-held configurator is also capable of monitoring the status of the flow sensors and the electronics. Any faults found are immediately displayed on its 4 line LCD display.
CM-800 Output and Display
The Model CM-800 provides three basic outputs: 4-20 mA analog output, factored pulse output for totalizer, and RS232/RS485. Also available with the CM-800 are fail-safe and high/low alarm relays. LCD rate and total display may be built into the enclosure and viewed through a window in the cover.
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