IFM PM1708 Pressure Transmitter

Modello completo: PM-,25BREA01-E-ZVG/US

Tipo di prodotto: Sanitary flush diaphragm relative pressure transmitter. Designed for food, beverage and pharmaceutical sanitary processes. Equipped with Aseptoflex Vario G1 external thread, cavity-free flush diaphragm, no dead space, suitable for CIP/SIP cleaning.

✅ Core Measurement Parameters

Campo di misura: -0.0125 ~ 0.25 sbarra (-12.5 ~ 250 mbar / -1.25 ~ 25 kPa)

Pressure type: Pressione relativa

Overload pressure: 0.6 sbarra (600 mbar); Pressione di scoppio: 30 sbarra

Factory preset: 0~250 mbar, 4…20mA analog output. Measuring range can be freely scaled via IO-Link.

Measuring element: Ceramic capacitive sensor

Precisione: Characteristic deviation ＜ ±0.2%FS; Repeatability ＜ ±0.1%FS; Long-term stability per year ＜ ±0.1%FS

⚙️ Mechanical & Wetted Specifications

Connessione al processo: G1 external thread (ISO228), Aseptoflex Vario sanitary seal

Wetted materials: 316l(1.4435) acciaio inossidabile, 99.9% alumina ceramic diaphragm; Ra＜0.4μm

Materiale dell'alloggiamento: 316L acciaio inossidabile; Peso: 273.45 G; Dimensioni: Φ30.2 × L111 mm

Installation torque: 35 Nm

Temperatura media: -25 ~ +150 ℃, supports high-temperature sterilization

Classe di protezione: IP67 / IP68 / IP69K, high-pressure washdown compatible (CIP)

Electrical connector: M12 A-coded 4-pin gold-plated plug

🔌 Electrical & IO-Link

Tensione di alimentazione: DC 18~30V

Produzione: 1 × 4~20mA analog + 1 × configurable digital switch output, IO-Link V1.1 COM2 (38.4kBaud)

Funzioni supportate: Zero/span calibration, internal temperature reading, diagnostic information. IO-Link resolution: 0.05 mbar

Tempo di risposta: 30ms for 2-wire mode; 7ms for 3-wire mode. Analog output damping adjustable from 0~4s

Features reverse polarity protection, short-circuit protection and watchdog circuit

📌 Typical Applications

Tank pressure and hydrostatic level measurement (low range) for food & beverage tanks; sanitary pressure monitoring in pharmaceutical processes; fermentatori, fruit juice/dairy, sauce media (solids-containing, viscous media; flush diaphragm minimizes material buildup).

🔁 Alternative Selection & Stessa serie

PM17 series with identical housing: PM1789 (smaller measuring range); PM17xx series shares same housing with different pressure ranges.

Alternative domestiche: Sanitary flush diaphragm transmitters with G1 thread, 316L wetted parts, 4-20mA+IO-Link for low pressure. Match overload pressure, burst pressure and surface roughness during selection.

⚠️ Installation & Note sulla manutenzione

1. Flush diaphragm surface must be flush with tank inner wall to avoid liquid trapping dead zones.
2. Strictly limit installation torque to 35 Nm; over-torque will damage ceramic diaphragm.
3. Keep temperature transients during CIP cleaning within specification; never exceed burst pressure.
4. IO-Link can read internal sensor temperature and diagnostic information for predictive maintenance.

IFM PM1708 Troubleshooting Checklist

Applicable for no output, pressure drift and abnormal alarms. Distinguish between 4-20mA analog signal and IO-Link digital signal. Power supply DC18~30V.

1. No Output (Ammeter / PLC channel shows 0mA or fixed 4mA)
2. Energia & Wiring Check (Highest Priority)

Alimentazione elettrica: Verify terminal voltage DC18~30V. Voltage drop under load shall not fall below 18V. Severe power supply ripple may also cause failure to start.

M12 4-pin A-coded pinout:

Perno1: BN Brown = +24V supply

Perno2: BK Black = 4~20mA / IO-Link signal

Perno3: BU Blue = 0V GND

Perno4: GY Grey = Switch output

Fault points:

Polarità inversa: Reverse power connection will not burn the sensor, but results in no operation and no output. Correct wiring to restore function.

Cortocircuito: Signal wire shorted to ground → current locked, PLC reports channel fault. Disconnect sensor to test wiring separately.

2-filo / 3-wire confusion: PM1708 is a 3-wire device. Do not wire as conventional 2-wire transmitter; this easily causes abnormal signals.

Misurazione: Disconnect load and measure supply & signal directly at sensor pins, to differentiate fault between sensor body or downstream PLC module.

2. Hardware Damage / Installation Issues

Water ingress / corrosion at M12 plug: Rated IP69K, but aged seal causes reduced insulation under humid conditions. Inspect pins for oxidation or water stains.

Mechanical overload: Installation torque >35Nm leads to microcracks on ceramic diaphragm. Diaphragm damage usually accompanied by zero drift; severe cases result in total loss of output.

Frozen medium: Medium temperature below specification causes diaphragm damage.

3. IO-Link Communication Failure

Velocità di trasmissione: COM2 (38400). Master station parameters must match.

Check master power supply and port enablement. Excessively long cables or poor shielding cause handshake failure.

Ripristino delle impostazioni di fabbrica: Send reset command via IO-Link master to restore sensor parameters.

1. Pressure Drift (Zero drift, inaccurate readings; value slowly changes while pressure remains constant)
2. Deriva zero (Più comune)
3. Installation stress drift

Over-tightened G1 thread creates continuous stress on ceramic diaphragm, leading to slow drift even at rest. Non eccedere mai 35 Nm.

Pipeline thermal expansion / contraction pulls sensor housing and introduces mechanical stress. Loosen thread, rest for 10 min, then re-perform zero calibration for verification.

2. Deriva della temperatura

Large medium temperature fluctuation outside compensation range. Read internal sensor temperature via IO-Link and compare with process temperature.

Short-term drift during CIP/SIP hot-cold cycling is normal thermal effect. If readings fail to recover after cooling, diaphragm damage is suspected.

3. Zero offset

Residual process material coats flush diaphragm; viscous or crystallized deposits block pressure transmission. Clean diaphragm surface.

Perform zero calibration via IO-Link under fully vented zero-pressure condition.

2. Span Drift / Readings too high or too low

Verify range parameters in IO-Link: Check whether upper/lower limits have been modified accidentally. Original PM1708 range: -12.5~250 mbar.

Overload damage: Instant pressure exceeding 0.6bar overload rating permanently damages ceramic element. This type of drift cannot be fixed by zero calibration; sensor replacement required.

Hydrostatic installation offset: Hydrostatic head from mounting height for level measurement is not compensated at zero point.

3. Interference-induced Drift

Power cables routed alongside sensor signal wires cause electromagnetic interference. Use shielded signal cable with single-end grounding for shield.

Poor 24V power quality with high ripple leads to jitter and drift on analog signal.

III. Alarms / Abnormal Status (IO-Link diagnostic bit alarm, or analog output locked at fault current)

Fault current for PM1708 is configurable; typical values: 3.6mA (low fault) or 22mA (high fault)

Read IO-Link diagnostic code first to classify fault:

1. Hardware Fault (Sensor Fault): Internal measuring element failure. Zero/span calibration impossible. Replace sensor directly.
2. Temperature alarm: Internal sensor temperature out of operating range (-25~150℃), caused by over-temperature during CIP or sustained high heat.
3. Pressure out-of-range alarm: Process pressure exceeds configured range. Not sensor damage; verify actual process pressure.
4. Parameter error alarm: Incorrect parameter download or invalid range setting. Restore factory defaults and reconfigure.
5. Communication fault: IO-Link cable break or master port fault. Only digital communication fails; analog output may still operate.
6. Fast On-site Troubleshooting Sequence (Follow in order)
7. Spegnimento, inspect M12 plug exterior, pin corrosion and water ingress; recheck wiring definition.
8. Power on under no-load condition, measure supply voltage and confirm DC18~30V.
9. Read pressure value under zero-pressure condition:

Stable reading near zero → zero point OK.

Large zero offset and calibration failure → mechanical stress or diaphragm damage.

4. Apply known reference pressure (calibrator) for verification:

Calibration successful → drift caused by installation stress or material coating.

Drift persists after calibration → sensor element damaged.

5. Read internal temperature and diagnostic codes via IO-Link to locate fault source.
6. After eliminating external factors, swap with a spare identical sensor to confirm body fault.
7. Idee sbagliate comuni
8. Idea sbagliata: Flush diaphragm can be scrubbed hard.

Alumina ceramic is wear-resistant, but sharp objects create irreversible scratches. Only gentle flushing is allowed for cleaning.

2. Idea sbagliata: Repeated zero calibration fixes drift.

Frequent calibration only masks mechanical stress or cracked diaphragm; drift will reappear shortly.

3. Idea sbagliata: Drift after CIP high temperature equals sensor failure.

Cool down to ambient temperature before assessment; temporary drift from thermal shock is normal.

1. Spare Part Replacement Criteria (Replace if any condition met)

Zero calibration fails, IO-Link reports hardware fault

Drift cannot be eliminated after pressure overload or over-torque installation

Visible cracks or chipping on diaphragm

Water ingress and corrosion inside M12 connector with degraded insulation

IFM PM1708 Ceramic Diaphragm (Measuring Cell) Damage Assessment

PM1708 uses oil-free ceramic capacitive flush diaphragm. Materiale della membrana: 99.9% alumina ceramic. Microcracks are invisible to naked eye. Assessment follows four steps: Visual Inspection → IO-Link Diagnostics → Zero / Calibration Test → Reference Pressure Comparison.

1. Ispezione visiva (Only detects obvious breakage; microcracks cannot be seen)

Remove sensor, clean ceramic diaphragm surface and inspect under strong light:

1. ✅ Normale: Uniform matte white ceramic surface, no scratches, chipping, indentation or radial cracks. Diaphragm surface flush with G1 end face.
2. ⚠️ Damage signs:

Chipping, radial fine cracks or pitting on ceramic surface

Indented / bulged diaphragm (from overload impact)

Gap between ceramic and stainless steel base, or medium penetration traces

Nota: Minor microcracks cannot be seen visually, and must be verified electrically or via pressure test.

Do not use hard tools to scrape ceramic surface during inspection.

1. IO-Link Diagnostics (Highest Priority, built-in measuring cell monitoring)
2. Read IO-Link diagnostic event: CELL Err (Measuring Cell Error). This indicates damaged ceramic capacitive element; diaphragm is damaged and cannot be repaired.
3. Fault characteristics:

Persistent fixed offset; sensor detects abnormal capacitance characteristics and reports CELL Err.

Some cases trigger hardware fault alarm, analog output locks to fault current (3.6mA /22mA).

No CELL Err ≠ intact diaphragm. Minor damage may only produce zero drift without CELL Err at early stage.

III. Zero Point Test (Most commonly used on-site method)

Prerequisito: Sensor removed, diaphragm fully exposed to atmosphere, zero pressure condition. Rest 10 minutes to release installation stress.

1. Read pressure value via IO-Link and record zero reading.

Normale: Stable zero reading with small deviation; zero calibration completes successfully.

Suspected damage:

Large zero offset and zero calibration failure (non-convergent calibration with error)

Recurring zero drift: Reading drifts minutes after successful calibration

Reading changes when flipping sensor orientation: Ceramic unit capacitance already compromised.

Differentiation: Installation stress drift — zero can be calibrated normally after loosening thread and resting. Diaphragm damage: zero cannot stabilize or be calibrated regardless of resting time.

1. Reference Pressure Calibration (Final confirmation, lab / calibration bench)

Apply known calibrated pressure (cover range: 0, 100mbar, 250mbar) and record readings:

1. ✅ Intact: Good linearity, good repeatability, small hysteresis between pressurization and depressurization; reading returns to zero after pressure release.
2. ❌ Typical diaphragm damage symptoms:

Nonlinear pressure-reading curve; mismatch between pressurization and depressurization curves

Readings high/low during pressurization; zero fails to return after depressurization

Poor repeatability: Large reading variation for repeated tests at same pressure.

Once observed, ceramic diaphragm has developed microcracks, non-repairable; sensor replacement required.

1. Typical Root Causes for Diaphragm Damage (for cross validation)

Installation torque＞35Nm, squeezing ceramic unit (most frequent cause)

Instant pressure exceeding 0.6bar overload rating, pressure shock

Vacuum shock, repeated severe thermal shock during CIP/SIP

Hard object impact on ceramic diaphragm (during cleaning or disassembly)

1. Quick Decision Rules (Direct application)

Replace ceramic diaphragm / sensor if any condition satisfied:

1. IO-Link reports CELL Err / measuring cell hardware fault
2. Zero calibration fails under zero-pressure condition
3. Reference pressure test: zero cannot recover after pressurization / depressurization, nonlinearity, poor repeatability
4. Visible cracks or chipping on diaphragm

If the following applies, diaphragm is NOT damaged (external factor)

Zero drift, but zero calibration succeeds after loosening thread and resting → mechanical installation stress, not cracked diaphragm.

VII. Idee sbagliate comuni

1. Idea sbagliata: Ceramic is hard and cannot break.

Ceramic is wear-resistant, but vulnerable to impact and compressive load. Over-torquing is the top cause of invisible internal microcracks.

2. Idea sbagliata: Pressure reading available = intact diaphragm.

Microcracks may still return pressure readings at early stage, only showing drift; CELL Err alarm appears later.

3. Idea sbagliata: Zero calibration can repair diaphragm.

Offset caused by microcracks is permanent damage. Calibration only temporarily masks drift, which will recur.

IFM PM17xx Same Series List (Identical housing as PM1708: Aseptoflex Vario G1 external thread, ceramic flush diaphragm, 4-20mA+IO-Link, IP69K, M12 a 4 pin)

Common features: Identical outline dimension, installation torque 35Nm, wetted material, electrical interface and diagnostic logic. Only measuring range differs. Meccanicamente intercambiabile (only IO-Link range parameters need reconfiguration).

Similar Housing Alternative Series (Compatible with Aseptoflex adapter)

PI17xx (Aseptoflex G1 flush diaphragm, similar appearance with LED status indicator)

PI1708: Same range as PM1708 (-12.5~250 mbar), con indicatore LED, other parameters similar. Preferred field replacement option for PM1708.

PI1717 / PI1707 / PI1703: Corresponding PM17 range versions with LED display.

PY Series (Sanitary flush diaphragm, oil-filled metal diaphragm, not ceramic, better high-temperature resistance for CIP)

PY20xx: Metal diaphragm, suitable for higher temperature and high pressure shock media. Diaphragm principle differs; fault diagnosis logic is not equivalent to PM17 ceramic diaphragm.

Replacement Selection Notes

1. All PM17 models use ceramic diaphragm same as PM1708; identical troubleshooting method. Mechanical interface fully compatible. Reconfigure range via IO-Link after swap.
2. PI17xx: Added LED indicator; meccanico, elettrico, installation torque and Aseptoflex seal remain unchanged. Widely used for project replacement of PM1708.
3. PY series uses oil-filled metal diaphragm, not ceramic. Diaphragm damage judgment method differs, not recommended as direct equivalent for PM17.

Not Recommended for Mixing

PM16 series: Filettatura G1/2, different process connection, cannot use PM17 Aseptoflex Vario adapter.

PI27/PI28: Local digital display, longer housing, different installation dimension.

Quick Selection Advice

Replace PM1708: Prefer PI1708 (same range, GUIDATO, compatible interface)

Same housing upgrade for higher micro-pressure: PM1718

Smaller micro-pressure range: PM1789