Switching unit for conductivity sensors

Switching unit for conductive sensors

Nivotester FTW325

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    • Easy wiring with terminal blocks

    • Configurable sensitivity range

    • Intrinsically safe signal circuit EEx ia IIC for using sensors in

      hazardous areas


    Specs at a glance

    Function Switching unit
    Product Liquids ≥ 5 µS/cm

    ATEX II (1) GD EEx ia

    CSA IS Cl.I,II,III Div.1

    FM IS Cl.I,II,III Div.1

    Feeding sensors Conductive rod or rope sensors

    Nivotester FTW325

    Product / VersionPrice / pcs. in USDOrder code
    ApprovalPower Supply1 to 34 to 1011+
    Non-hazardous area85-253VAC193.-180.-170.- FTW325-A2A1A
    20-30VAC/20-60VDC193.-180.-170.- FTW325-A2B1A
    ATEX II (1) G [Ex ia Ga] IIC, WHG ATEX II (1) D [Ex ia Da] IIIC, WHG85-253VAC255.-237.-225.- FTW325-C2A1A
    20-30VAC/20-60VDC255.-237.-225.- FTW325-C2B1A


    Product / VersionPrice / pcs. in USDOrder code
    Housing Field, R4 182x180x165, 5xM20, PC Protection housing Minitec. Synthetic housing with transparent cover. Protection IP66. 4x22.5mm / 2x45mm. Usage: FTL825.103.82 52010132

    Prices valid until 31.12.2020 in USD per unit (not including shipping and applicable sales tax). See
    Endress+Hauser Terms and Conditions

    Is this Liquipoint level switch not the perfect match for your application?

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  • Application

    The Nivotester FTW325 can be used for overspill protection (WHG), pump dry running protection or as a two-point control for pumps. Sensors such as the Liquipoint T FTW31/FTW32 can be connected to the FTW325. Multipoint detection for up to five measuring points is possible by using 3 Nivotester FTW325s.


    The intrinsically safe signal input of the limit switch Nivotester FTW325 is galvanically isolated from the mains and the output. The Nivotester supplies the conductivity probes with an alternating current via a two or three-wire line and monitors its voltage. If the product reaches the switch point of the probe, the voltage between the probe and Nivotester is reduced. The output relays at the Nivotester switch depending on the set failsafe mode. Two yellow LEDs on the front panel of the Nivotester indicate the relay switch status.

    Application Example

    Switching unit - FTW325 - Application example

    a) FTW325 - Probe rod1


  • Technical data

    Measured variable Depending on the setting selected, the limit signal is triggered at a minimum or maximum level
    Measuring range Three resistance ranges can be set with DIL switches; 0.1 to 1.0 kΩ; 1.0 to 10.0 kΩ; 10.0 to 200.0 kΩ
    Input signal Input galvanically isolated from power supply and output
    Type of protection [EEx ia] IIC
    Output signal Relay output: one floating changeover contact for the level alarm
    Alarm relay Floating changeover contact for fault reporting, can be switched as second level relay
    Switching delay 0.5 s; 2.0 s; 6.0 s when relay energized
    Switching power of relay contacts

    U~ max. 253 V;
    I~ max. 2 A;
    P~ max. 500 VA at cos φ ≥ 0.7;

    U– max. 40 V;
    I– max. 2 A;
    P– max. 80 W

    Function indicators Light emitting diodes for operation (gn), fault (rd), level alarm 1 (ye) and level alarm 2 (ye) light up when level relay is energized
    Power supply
    Supply voltage

    85 to 253 V AC, 50/60 Hz;

    20 to 30 V AC / 20 to 60 V DC, max. 60 mA

    Power consumption

    AC-version maximum 4.5 VA

    DC-version maximum 1.2 VA (at Umin 20 V)

    Operating conditions
    Ambient temperature For individual mounting -20 to +60 °C for series mounting without lateral spacing -20 to +50 °C (-4 to +122 °F)
    Storage temperature –25 to +85 °C (–13 to +185 °F) (preferably at +20 °C/+68 °F)
    Installation in protective housing –20 to +40 °C (–4 to +104 °F)
    Ingress Protection IP 20
    EMC Interference emission to EN 61326; electrical equipment Class B; interference immunity to EN 61326; Annex A (industrial) and NAMUR recommendation NE 21 (EMC)
    Electrical connection
    Connection line two core, screening not required
    Line resistance max. 25 Ω per core
    Cross-section max. 1×2.5 mm² or 2×1.5 mm²
    Ex approval ATEX II (1) GD [EEx ia] IIC
    CSA IS Cl.I,II,III Div.1
    FM IS Cl.I,II,III Div.1

    Dimensions (in mm)

    Switching unit - FTW325 - Dimensions

    Mounting on DIN rail (EN 60715 TH35)


    Installation according to instruction manual

    Electrical connection

    Switching unit - FTW325 - Connecting


    b) Power supply

    c) Level relay 2/Alarm relay

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