Overview
Preamplifiers
The standard output from a turbine meter is a zero-voltage centered alternating current sine wave that is typically less than one volt ac peak to peak and can be as low as 20 mV p-p ac. The current flow is low micro-amps. Small diameter meters near their minimum flow capacity produce the lowest amplitudes. If there is other electrical equipment in the area, then electromagnetic noise or grounding issues can induce small pulses on the interconnecting wires that the totalizer can mis-interpret as flow pulses. An amplifier (preamp) mounted on or very close to the turbine flow meter increases the magnitude of the legitimate pulses so that the pulse receiving device can reject the illegitimate pulses as background noise. All remote signal cables must be shielded.
Specifications
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The MC-III MC Synergy Preamp function
Every MC-III and MC Synergy totalizer have pre-amplifier output circuits called AMP & SQUARE. This output has no adjustment or calibration since it defined by the internal circuit as “one pulse out for one pulse in”. It replicates and retransmits the raw input frequency coming into the totalizer from the flow meter with zero latency. These are often used to prove pulse-producing flow meters in the field or to take into a SCADA system for analysis. It can also be used to transmit the raw signal over long distances.
The preamp output from either the MC-III and MC Synergy is an open drain transistor. The MC-III can switch up to 50 mA from an external power source of between 5 to 30 VDC. The MC Synergy can switch up to 60 mA from an external power source of between 6 to 27 VDC.
While it may seem odd to apply such capable devices for its pre-amp capabilities, if there is to be local indication and/or connectivity to a SCADA system, the embedded AMP & SQUARE option allows it to be economical. The MC-III and MC Synergy are offered with international certifications as well as optional stainless steel enclosure.
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Amplified pick-up coils
Powered pickup coils offer an output very similar to the MC-III. They can be an effective option provided,
- The temperature is not unusually high or low
- They are not subjected to excessive vibration
- The quantity required is more than ten
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NUFLO TMP-100 Pulse Divider Circuit
This OEM style circuit board product is designed to provide a pulse output representing a user-defined unit volume from a remote mounted turbine meter. The output can be a optically isolated solid state type or an electromechanical type.
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