Emerson 20/20 service manual Motor Current, Remote Capacity

Section 13 • Instruments Calibration

devices are predefined and if one is selected, then all the setpoints will be set for the operator.

Custom Device:

•This option allows the operator to choose the mini- mum and maximum value of the instrument being used.

Offset:

•Once the two point calibration is completed, it is not uncommon for there to be a small error. By entering the value of the error from the calibrated value and the actual value into the adjustment entry box, that error will be added/subtracted from the total offset. The offset is applied to the calibrated value which should correct the error.

Range:

•This option is available when the custom device op- tion is chosen. Here the operator defines the signal type and range transmitted by the instrument. The operator can choose from several predefined ranges in the drop-down box or enter a value.

Motor Current

The Vission 20/20 has two options for measuring motor current. A 4-20mA signal transmitted from an external device or a 0-5Amp AC current Transformer. The type of device being used is selected in the configuration screen.

The motor current tab has the ability to calibrate both measurement options through the 4-20mA scale and current transformer ratio sections. However, the device type that is selected in the configuration screen will be the only section that will be available to the operator.

The calibration differs from all other calibration proce- dures in that the motor current must be calibrated while the compressor is running at close to full load amps as possible. In addition, the operator will need to enter a value into the “Enter Desired Value” entry box that is equal to the measured value in amps by a calibrating measurement device. After entering the measured val- ue, the displayed motor current may still be off slightly. In this case reenter the desired value and the displayed value should get progressively closer.

4-20mA Scale:

•4mA:

•Not editable by the operator. Defines the minimum value in amps represented by a 4ma inputs.

•

•20mA:

•Defines the maximum value in amps repre- sented by a 20ma inputs.

•Enter Desired Value:

•The operator enters the correct current value. Each entry will recalculate the point-slope calcu- lations of the current calibration.

•Total Error:

•Not editable by the operator. Displays the to- tal error offset of entries from the “Enter Desired Value” setpoint.

Current Transformer Ratio:

•Primary

•Defines the upper value of the current transformer.

•Secondary:

•Not editable by the operator. Defines the minimum value of the current transformer.

•Enter Desired Value:

•The operator enters the value of the cor- rect current value. Each entry will recalculate the point-slope calculations of the current calibration.

•Total Error:

•Not editable by the operator. Displays the to- tal error offset of entries from the “Enter Desired Value” setpoint

Remote Capacity

The remote capacity input allows a system controller such as the PLC to control the capacity position during direct I/O control.

Control Input:

•This drop-down box is not used at this time. Scale:

•Defines the minimum and maximum Capacity posi- tion between 0% & 100% for the 4-20ma input.

Offset:

•Used to correct any error in the capacity position. By entering a value into the Adjustment entry box, that value will be added to the total offset displayed in the “total offset” entry box.

13 – 2 Vission 20/20 • Operation and Service Manual •Vilter/Emerson • 35391SC 1.8.5153