The UVM takes a 0 V to 10 V signal from the third-party equipment, and depending on the scaling setting, interprets this as a 0 CFM to xxxx CFM request signal. The UVM is pre-programmed with the associated valve’s linearization curve and moves the valve’s actuator to the correct position for the requested CFM.
Each valve is fitted with an electronic position sensor on the lever arm at the point of entry into the valve body. The electronic position sensor is used to provide actual valve position information to the controllers. This signal is non-linear and has a random 0% and 100% position voltage.
The UVM converts the sensor signal to a position on the valve and then translates that to a CFM value. The CFM value is in turn output from the UVM as a 0 V to 10 V signal at the same scaling as the CFM request signal.
The 0 V to 10 V signal is processed by the valve’s calibration settings as set by the factory. The subsequent signal is then converted to an equivalent CFM request value. This value is dependent on settings provided by the factory as applicable for the associated valve size.
The factory default settings relative to valve size are:
- 8 in. valve 10 V = 800 CFM
- 10 in. valve 10 V = 1100 CFM
- 12 in. valve 10 V = 1600 CFM
- 14 in. valve 10 V = 2300 CFM
The factory applies the equivalent CFM request value to the calibration curve for the associated valve and an equivalent valve position value is generated.
This position value is applied to the actuator output voltage calibration section and output to the actuator. The result is that the actuator moves to the required position so that the valve passes the requested CFM.
As the valve moves to position, the position feedback sensor moves as well. The signal from this sensor is processed by a sensor voltage to position calibration section. The output of this section provides an accurate position value. The position value is applied to the position to CFM mapping table and an equivalent CFM value is outputted.
This CFM value is passed through CFM to voltage scaling factor and converted to a voltage value. The voltage value is passed through the factory set output calibration section and made available to the voltage output for use by the third-party equipment as the actual valve CFM.
In certain circumstances, the feedback signal does not match the requested CFM signal. If 0 CFM is requested, the input is 0 V and the valve is closed to the minimum CFM that it can attain. This value is not 0 CFM and for a 12 in. valve is approximately 90 CFM. In this case, the feedback signal is the equivalent of 90 CFM or 0.56 V for a 10 V = 1600 setting.
If a UVM for an 8 in. valve is set with an arbitrary scale of 10 V = 1100 CFM (or 110 CFM/V), and a request signal of 9 V (or 990 CFM) is input into the unit, the actuator increases to 100%, as the maximum is 700 CFM. The voltage feedback output signal is approximately 6.4 V, the actual valve CFM is approximately 700 CFM.
For more information on basic UVM functionality, see the following image .