Engine News SEBD9414, 25 September 2006, "Calibration of the 175-4998 Signal Converter ". The original article has been revised to add effectivity. Also, the part number of a wicking sealant was canceled. Refer to the effectivity above and the information below.
Illustration 1
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A new calibration procedure is now used on the 175-4998 Signal Converter. The new calibration procedure adjusts both of the potentiometers on the signal converter. The new procedure also secures the offset potentiometer in place once the adjustments have been made. The procedure ensures that the signal converter is properly calibrated. A functional test that verifies the zero, the middle point, and the maximum of the performance curve is performed at the factory. The functional test checks the operation of the 175-4998 Signal Converter. The effective date of the functional testing is 11August 2006.
Calibration Procedure for the 175-4998 Signal Converter Table 1 Required Tools Part Number
Tool
146-4080
Digital Multimeter Gp
9S-3263
Thread Lock Compound
n/a
Loctite Threadlocker 290 50mL
n/a
0 – 200 mA Current source
NOTICE Do not exceed 230 mA of current into the converter input. Electrical damage to the module will occur.
1. Remove electrical power from the Electronic Instrument Panel (EIP).
Illustration 2
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Typical example (1) "OFFSET" potentiometer (2) "SPAN" potentiometer
2. Remove the input wire for the system and any input signal that is c onnected to terminal 1 of the converter. Note: Do not remove the wires from terminal 10 or from terminal 12. Terminal 10 and t erminal 12 are the outputs for the converter. For proper operation of the converter, terminal 10 and terminal 12 must remain connected to the Electronic Control Module (ECM). The converter w ill not function without completing the above circuit.
3. Restore power to the EIP.
4. Use the 146-4080 Digital Multimeter Gp to measure the duty cycle of the converter output. The duty cycle of the converter output is measured across terminal 10 and terminal 12. 5. Verify that the input wire is disconnected from terminal 1. Adjust "OFFSET" potentiometer (1) in order to provide a 5 percent duty cycle. Once the potentiometer is set for an output of 5 percent duty cycle, apply Loctite Threadlocker 290 in order to secure the potentiometer in place. Securing the potentiometer at 5 percent will ensure that the offset is calibrated correctly. Note: When an external current source is used for testing, disconnect the signal lines from the Silicon Controlled Rectifier (SCR). Also, do not operate the engine when you are using the external current source. Accidental high current surges may produce an engine overspeed.
6. Use a 0 – 200 mA current source. Apply a full 200 mA signal to terminal 1 and to terminal 3 of the 175-4998 Signal Converter. Adjust "SPAN" potentiometer (2) in order to achieve a reading of 85 percent ± 2 percent duty cycle. Table 2 Correlation of Input to Input Input (Milliampere)
Output (percent duty cycle)
0
5±2%
20
13 ± 2 %
60
29 ± 2 %
100
45 ± 2 %
160
69 ± 2 %
200
85 ± 2 % Table 3
Specifications
Input signal range
0-200 mA Direct Current (DC).
Output signal range
PWM 5-90%
Max input current
225 mA
Supply voltage
15-45 VDC
Temperature range
−40 °C (−40 °F ) to 85 °C (185 °F)
PWM frequency
485 Hz
PWM active state
Active high (external pull up to positive DC voltage
Adjustments
Span and offset
7. Repeat Step 3 through Step 6 until the duty cycle is adjusted to the values in Table 2. 8. Remove electrical power from the EIP. 9. Reconnect the signal wire or wires to terminal 1 of the converter.
Illustration 3
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(3) 7S-1198 Screws
10. Apply a small amount of 9S-3263 Thread Lock Compound to screws (3) . Torque for the screws (3) Torque ... 1.7 ± 0.25 N·m (15 ± 2 lb in) 11. Restore power to the EIP. 12. Start the engine and operate the engine. Note: The engine speed is now controlled by the 0-200 mA signal.
