Application and Installation Guide EMCP 4 SCADA Data Links
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This verifies that each key-press adjusts the percentage by 0.5% (since we did ten key-presses). Now we
can check the actual voltage command that is sent to the AVR by reading the Desired Genset Output
Voltage register.
Request: 0x 01 03 04 20 00 01 xx xx
0x 01 = slave address of EMCP 4
0x 03 = function code (Read Registers)
0x 04 20 = Desired Genset Output Voltage
0x 00 01 = register count
Response: 0x 01 03 02 01 EA xx xx
0x 02 = byte count (2 bytes = 1 register)
0x 01 EA 490V desired
This is correct. because the Total Bias Percent represents a percentage of 40% of rated, which is 192,
the overall bias percentage is 5% of 192, which is 9.6 and rounds up to 10. 480 + 10 = 490V.
Using the Total Voltage Bias Percent Increment Command Modbus register, re-adjust the desired voltage
to nominal, which is 480V. This time however, we want to increment the bias by -5% (negative five
percent) since the current bias is 5%.
Request: 0x 01 06 04 22 7B 00 xx xx
0x 01 = slave address of EMCP 4
0x 06 = function code (Write Register)
0x 04 22 = Total Voltage Bias Percent Increment Command
0x 7B 00 = 31488 (divide by 128) = 246 (-251 offset) -5%
Response: 0x 01 06 04 22 7B 00 xx xx
0x 04 22 – echo of address
0x 7B 00 – echo of data
Finally, re-check the Total Voltage Bias Percent to verify that the bias has returned to zero.
Request: 0x 01 03 04 21 00 01 xx xx
0x 01 = slave address of EMCP 4
0x 03 = function code (Read Registers)
0x 04 21 = Total Voltage Bias Percent
0x 00 01 = register count
Response: 0x 01 03 02 7D 80 xx xx
0x 02 = byte count (2 bytes = 1 register)
0x 7D 80 32128 251% (-251% offset) 0.0% bias
7.8 READING ANALOG INPUTS
The EMCP 4 analog inputs are fully configurable. This means that the sensing type is configurable, as
well as the usage of the analog input, as well as the scaling of the sensor reading (based on sensing
type, such as voltage, current, or PWM percentage) into measured (real-world, such as a pressure in
kPa) data units. The configuration of an analog input is determined by a set of setpoints. Refer to the
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