Applicable to: 3300XL series probes (8/11/14mm) + 330180 series proximitors, paired with 3500 vibration/displacement monitoring cards. The process is divided into 5 steps from simple to precise: visual preliminary inspection → power-off electrical testing → power-on voltage verification → TK-3E professional calibration → 3500 system alarm verification, to quickly locate faults.
I. Visual Physical Inspection (First Step, Power-Off Operation)
Probe Check
End face: No dents, scratches, corrosion or oil accumulation; the ceramic sensing surface is intact without chipping. If the end face is damaged, the coil is most likely damaged, and the probe is directly judged as defective.
Cable/connector: The tail cable has no skin breakage, bending or aging; the BNC coaxial connector has no oxidation, deformation or water ingress; the thread has no thread slipping.
Preamplifier Check
The housing has no deformation, water ingress or oil corrosion; the wiring terminals have no ablation or blackening.
Complete marking: Confirm the total marked cable length of the proximitor (5m/9m/14m). The total length of the probe tail cable plus the extension cable must match, otherwise the sensitivity will fail.
Extension Cable
The coaxial outer sheath is free of damage; the BNC connectors at both ends have no water ingress or bent pin cores; the intermediate connector is well sealed without oil seepage.
II. Power-Off Electrical Measurement (Multimeter + Megohmmeter, Distinguish Probe/Cable Faults)
Probe Coil Conduction Resistance (Multimeter Resistance Mode) Disconnect the probe from the extension cable, measure the resistance between the BNC inner core and the shielded outer shell of the probe:
Qualification standard: 8mm probe 5～15Ω; 11/14mm probes have similar ranges, deviation ≤5% of the original factory value.
Fault judgment:
Infinite resistance: Internal coil open circuit, probe scrapped.
Resistance ≈0Ω: Coil short circuit, probe scrapped.
Resistance far exceeds 15Ω: Lead wire breakage or poor contact.
Probe Insulation Resistance (500V Megohmmeter) Measure the insulation between the probe inner core and the metal outer sheath/armored shielding layer:
Qualified: ≥100MΩ.
Fault: Insulation <5MΩ → The probe is damp, internal insulation breakdown occurs, leading to signal drift and jump.
Extension Cable Test
Conduction: The inner cores at both ends are interconnected (2～5Ω), the shielded outer sheaths at both ends are interconnected (0～1Ω); infinite resistance indicates wire breakage.
Insulation: Insulation between inner core and shielding layer ≥100MΩ, below the standard means the cable is broken and short-circuited.
Preamplifier Insulation Rough Test Insulation between the power supply terminal, output terminal of the proximitor and the housing ≥100MΩ. Too low insulation indicates that the internal circuit is damp and broken down.
III. Power-On Static Voltage Test (Distinguish Preamplifier Quality, Core On-Site Method)
Preamplifier wiring definition (three-wire system):
VT: -24V power supply negative (power supply range -17.5～-26VDC, reverse connection is strictly prohibited)
COM: Common reference ground
OUT: Gap voltage signal output (measure OUT and COM with multimeter DC mode)
Step 1: Confirm normal power supply first Disconnect the probe loop, only power on the proximitor, measure the voltage between VT and COM to be stable at -18～-24VDC; if there is no voltage/too low voltage/reversed polarity, deal with the power supply first, do not judge the sensor as damaged.
Step 2: No-load short circuit test (independently judge the quality of the proximitor) Disconnect the probe/extension cable, use a metal to short-circuit the BNC inner core and the shielding shell on the proximitor side:
Qualified output voltage: -0.6～-0.8VDC.
Fault judgment: Voltage not in the range, no voltage, or voltage follows the power supply voltage → The internal oscillation/demodulation circuit of the proximitor is damaged, replace it directly.
Step 3: Connect the probe to measure gap voltage (linear zero point verification) Align the probe with a clean carbon steel target surface, slowly push it to the linear midpoint (standard zero gap is about 1.27mm/50mil):
Normal zero voltage for 8mm probe: -9.0～-10.0VDC.
Slowly move the probe away from the target surface: The output voltage should rise smoothly towards -2V; when approaching the target surface, it should fall smoothly towards -18V, no jump or step in the whole process.
Corresponding abnormal voltage faults:
Output constant ≈-24V: Probe loop open circuit (wire breakage/loose connector/gap exceeds maximum linear range).
Output constant ≈0V: Probe/cable inner core short-circuited with shield.
Large voltage drift, frequent jump: Probe insulation damage, cable shield damage, proximitor aging.
Voltage changes irregularly, jumps in steps: BNC connector oxidation and poor contact.
IV. TK-3E Calibrator Professional Quantitative Judgment (Accurately Verify Sensitivity/Linearity, Mandatory for Annual Unit Inspection)
Match the bracket according to the specification, fix the probe on the micrometer displacement stage, fully connect the probe + matching length extension cable + proximitor, and connect to the standard -24V power supply.
Zero calibration: Adjust the micrometer to 50mil (1.27mm), the output voltage must fall within the standard zero point (-9.0V±0.5V).
Multi-point linear test (divide the full range of 0～80mil into 4 equal points): The standard sensitivity of 8mm probe is 7.87V/mm (200mV/mil), the voltage error at each point ≤±0.5% full scale is qualified.
Fault judgment: Linear deviation exceeds the standard, sensitivity drift >10%: Probe coil aging or proximitor circuit drift. Non-linear curve, inflection point jump: Probe damage or proximitor damage.
V. 3500 System Card Status Alarm Auxiliary Judgment
Channel red light always on (hard fault Probe Fault): The 3500 card detects open circuit/short circuit in the sensor loop, most likely probe wire breakage, cable short circuit, no output from the proximitor.
OK green light flashes/goes out: Proximitor power supply abnormality or internal damage, loop self-check fails.
Large signal drift, fluctuation, over-range on the monitoring screen: Poor probe insulation, proximitor temperature drift fault, shielded ground interference.
Comparative replacement method (quick on-site troubleshooting): Interchange test channels with a confirmed intact probe + cable. If the fault moves with the probe → the probe is damaged; if the fault remains in the original channel → the proximitor or card is faulty.
VI. Quick Fault Summary Comparison Table
Fault Phenomenon Most Likely Damaged Component
Coil resistance infinite/0Ω Probe internal wire breakage/short circuit
Extremely low insulation resistance Probe/cable damp and skin broken
Output ≠-0.6~-0.8V after short-circuiting BNC Preamplifier damaged
Gap voltage changes without smoothness, constant value Cable open circuit/short circuit
TK-3E linearity/sensitivity severely out of tolerance Probe aging or proximitor drift
3500 channel continuous Probe Fault red light Loop open circuit/short circuit, locate by segmental resistance measurement
⚠️ Key Notes
The total length of the probe tail cable plus the extension cable must be consistent with the marked length of the proximitor, wrong length matching will directly lead to measurement failure.
The shielding layer is only single-end grounded at the proximitor side, and the shielding at the probe side is suspended, to avoid ground loop interference causing signal jump.
When the unit has interlock, be sure to cut off the vibration/displacement interlock before testing to prevent accidental tripping.
Distinguish "inappropriate installation gap" and "hardware damage": Adjust the gap and clean the connector first, then judge the component as scrapped.
Your message must be between 20-3,000 characters!
