Lake Shore 234, User Manual

Page: 33 / 49

Lake Shore Model 234/234D User’s Manual
Service 5-1
CHAPTER 5
SERVICE
5.0 GENERAL
This chapter covers General Troubleshooting in Paragraph 5.1, Model 234
Connectors in Paragraph 5-2, CalCurve Field Installation in Paragraph 5.3,
and Calibration in Paragraph 5.4.
5.1 GENERAL TROUBLESHOOTING
5.1.1 No Output (On-Board LED Off)
Verify output of external power supply is +5 VDC. If not, replace the supply.
If using the front panel input jack (J2), verify center post of connector coming
from power supply is NEGATIVE. If not, correct wiring. If using front panel
input jack (J2), verify external power supply is regulated at +5 VDC and can
supply a minimum of 500 mA. Also verify that OUT+ and SHIELD are
not
connected to each other.
Due to extensive protection circuitry installed in Model 234, all the above
problems eventually cause the 1 A slow blow fuse to burn out. After
correcting the cause, replace the blown fuse with identical size and type.
5.1.2 Output Stops Before Reaching Upper Limit
Normally caused by too high of a resistance from output monitoring device.
Absolute maximum acceptable resistance is 500
Ω
. Also verify that proper
range DIP switch is selected.
5.1.3 Resistance Readings Are Incorrect
Verify correct voltage and current connections to the sensor. Parasitic
resistances between the voltage and current connections inside the device
can make the resistance measurement incorrect if the leads are connected
incorrectly.
5.1.4 Open Condition
A sensor must be connected when power is applied. If not, an Open error
will be displayed even if a sensor is re-connected. A power cycle must be
performed with the sensor properly connected before the error will be
cleared.