Metrix ST5484E-121-010-00 Vibration Transmitter

(Often mislabeled as Hoerbiger)

ประเภทสินค้า: Seismic velocity vibration transmitter (2-wire 4-20mA, loop-powered). Used for vibration monitoring of bearing housings, ปั๊ม, fans and motor casings.

ยี่ห้อ: Metrix. NOT Hoerbiger. This transmitter is frequently supplied together with Hoerbiger components in compressor packages, hence the common confusion.

✅ Model Code Breakdown ST5484E-121-010-00

ST5484E: Series base model

121: Code for measuring range, frequency response and housing material

010: เต็มสเกล 10 มิลลิเมตร/วินาที (อาร์เอ็มเอส, vibration velocity)

00: ตัวเชื่อมต่อ / mounting option: 2-core flying lead, no auxiliary dynamic acceleration output (pure 2-wire 4-20mA)

Signal definition: 4mA = 0 มิลลิเมตร/วินาที; 20mA = 10 mm/s RMS

📌 Key Technical Specifications

🧩 Applications

Vibration monitoring on bearing housings of fans, ปั๊มหอยโข่ง, มอเตอร์, gearboxes and reciprocating compressors. 4-20mA signal connects directly to PLC/DCS AI analog input channels for vibration trending, alarm and interlock. Widely used in petrochemical, air separation and power plants.

📎 Compatible Accessories

8200 conduit elbow (mandatory for hazardous area explosion-proof installation)

7084 flange mounting adapter (thread to flat flange conversion)

Shielded twisted pair instrument cable (2-core shielded)

⚠️ Selection & หมายเหตุทดแทน

1. ความแตกต่าง: ST5484E (velocity 4-20mA transmitter) vs SW5484E (version with relay switch)
2. Three critical parameters to match for replacement: full scale mm/s, frequency response code, wiring configuration (with/without dynamic acceleration output)
3. ทางเลือกภายในประเทศ: Integrated piezoelectric vibration velocity transmitters. Explosion-proof certificate, mounting thread and frequency response curve must be matched.

📦 HS Customs Code Reference

90262090 (Transmitters for measuring / testing physical quantities such as pressure, ไหล, level and vibration)

Metrix ST5484E-121-010-00 Vibration Transmitter Troubleshooting Checklist

ใช้งานได้: 2-wire 4~20mA, 0~10mm/s RMS, ST5484E series. Three fault categories: ไม่มีเอาท์พุต, Current drift, Signal noise/jitter

Precaution for safety: Follow explosion protection rules in hazardous areas. Power off before wiring inspection. Avoid short-circuit loop tests to prevent transmitter / AI module damage.

Pre-check (Perform first for all faults)

1. Verify loop power supply: 18~28VDC (measure voltage directly at transmitter terminals, not only power cabinet reading)
2. Polarity check: Reversed polarity normally does not burn the 2-wire unit, but some AI modules cannot read reversed signals. สายไฟ: + to power positive, to AI module input
3. Loop total resistance check: AI module input resistance + cable resistance. Total load ≤500Ω (typical maximum load for ST5484E)
4. การตรวจสายตา: Damaged housing, condensation ingress, cracked cable jacket, corroded terminals. Loose mounting thread introduces false vibration readings.
5. Mounting base: Rigid mounting required. Gaskets / soft pads attenuate vibration and cause inaccurate readings. Clean rust on mating surface.
6. สิ่งแวดล้อม: Confirm temperature within -40~100℃. Strong cables for motors / VFDs routed in parallel nearby easily induce interference.

ความผิดพลาด 1: ไม่มีเอาท์พุต (Current locked at ~0mA / below 3.8mA)

ขั้นตอนการแก้ไขปัญหา

1. ปิดเครื่อง, check loop continuity

Disconnect wiring at both ends of transmitter. Do NOT judge transmitter health by measuring resistance of piezoelectric sensor with multimeter; static resistance is not fixed.

Cable check: Open circuit in 2 signal cores; shield must not short to signal conductors.

2. Standalone loop test (disconnect from DCS/PLC AI)

Simple test: 24VDC power supply in series with multimeter mA range directly connected to transmitter, bypass DCS.

Current ≈4mA: Transmitter healthy → fault on downstream DCS AI channel, terminals or scaling configuration.

Current ＜3.8mA or 0mA: Fault in transmitter / แหล่งจ่ายไฟ / สายเคเบิล.

3. Short circuit inspection

Short between signal cores brings loop current to zero; core-to-earth short also pulls down current.

4. Power voltage drop

Long cable creates voltage drop; terminal voltage below 18VDC will fail to power up transmitter.

5. Transmitter hardware failure

Damaged piezoelectric element or potting water ingress. Tapping transmitter housing produces no mA change: sensor likely failed.

Quick Conclusion

✅ 4mA present in standalone 24V test: Transmitter OK, fault in AI channel or wiring

❌ Still no current in standalone test: Cable open circuit / Transmitter failure

ความผิดพลาด 2: Current drift (Slow gradual rise/fall, no jitter, zero offset)

อาการ: Static equipment, current slowly deviates from 4mA; vibration unchanged but reading creeps up or down over time

1. Zero drift classification

Thermal drift: Slow offset during equipment heat-up / cool-down (inherent minor effect for piezoelectric sensors; large drift is abnormal)

การติดตั้งแบบหลวม: Unstable vibration transfer due to loose bolts; slow variation with thermal expansion. ขันให้แน่นตามแรงบิดที่กำหนด.

2. Loop load variation

Degraded AI module or oxidized terminal contact resistance changes loop voltage drop and causes mA drift; clean terminals.

3. Moisture ingress inside transmitter

Seal failure, moisture on PCB. Drift worsens progressively, later accompanied by jitter or total loss of output. Focus inspection on cable entry seal.

4. Incorrect DCS scaling

This model maps 0~10mm/s to 4~20mA. Wrong DCS range (เช่น. 0~20mm/s) causes apparent reading drift while raw signal is normal.

5. Mechanical resonance / base resonance

Thin weak mounting bracket resonates on stationary equipment and generates false vibration. Reinforce bracket rigidity.

6. Long-term aging

Piezoelectric element aging after years of service leads to persistent zero offset.

Quick Conclusion

ปิดเครื่อง, cool down fully then restart:

Zero returns close to 4mA: Thermal effect / mounting resonance suspected

Zero remains offset: Poor terminal contact / Transmitter moisture & ริ้วรอย

ความผิดพลาด 3: Signal noise & jitter (Fast current fluctuation, stable actual machine vibration)

อาการ: Stable machine vibration, random mA jumps, noisy DCS trend curve

1. โล่ & การต่อสายดิน (Most frequent root cause)

✅ Correct practice: Shield single-point earthed at DCS cabinet end. Shield at transmitter end must be floating. Dual-point earth creates ground loop and power frequency interference.

Shield touching signal conductors or multiple earth points is top cause of jitter.

2. Cable routing

Instrument cable laid parallel with VFD / motor power cables. Separate by ≥30cm, cross at 90° where crossing required.

Use 2-core shielded instrument cable, ordinary unshielded cable is not acceptable.

3. Power supply ripple

Degraded 24V DC supply with high ripple. Add filter at power side or replace regulated power supply.

4. Ground potential difference (Ground loop)

Transmitter mounted on motor casing; motor frame and cabinet earth have potential difference, generating ground loop current and severe signal jitter. Isolate casing earth.

5. Mechanical causes

Loose bolts, sand/rust on mating surface causing unstable sensor contact. Clean mounting face and tighten to torque.

6. DCS AI filter setting

Too short AI input filter time passes interference directly to display. Increasing software filter only masks symptom; hardware interference must be resolved first.

7. Transmitter hardware defect: PCB solder joint intermittency, random jitter under vibration.

Quick Conclusion

Temporarily disconnect shield earth at cabinet:

Jitter significantly reduced: Ground loop / wrong shield earthing

Jitter unchanged: Power cable interference / supply ripple / transmitter internal fault

Field Quick Test Procedure (Recommended sequence)

1. Measure DC voltage at transmitter terminals (Confirm 18~28V)
2. Disconnect DCS side, test transmitter with standalone 24V supply + mA meter
3. Lightly tap transmitter housing and monitor mA reading:

mA rises smoothly when tapped, falls on release: Sensor basically functional

No mA response when tapped: Sensor failed

Erratic jumping on tapping: สายไฟหลวม / internal bad solder joint

4. Check shield earthing and confirm single-point earth
5. Check mounting bolt tightness

Fault Reference Table

Important Cautions

1. Do not apply high voltage to transmitter. Do NOT use megger to test signal cable (will damage piezoelectric element)
2. This transmitter measures housing vibration, NOT shaft vibration (shaft vibration uses eddy current probes)
3. For hazardous area, power down equipment before opening cover or disassembly; comply with explosion protection requirements.