Wiring - HMT370EX

HMT370EX User Guide

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User guide
WARNING Protected installation using galvanic isolators or Zener barriers is mandatory in a hazardous environment.
Galvanic isolators and Zener barriers are available from Vaisala as accessories. See Spare parts and accessories.
CAUTION Ensure that the transmitter is powered correctly. 12 V DC is the minimum voltage in all conditions, measured at the transmitter screw terminals. If the supply voltage is less than 12 V DC, the analog output current can be erroneous.
It is recommended to use ferrules on the stripped wires to help ensure a secure connection with the screw terminals.
Figure 1. Wiring example using one cable
  1. Prepare the cabling wires as required in your application (cabling either through 1 or 2 lead-throughs).
    1. Strip the cable wires: it is recommended to attach ferrules to the contact ends of the wires.
    2. Open the cable gland and insert a suitable length of the cable inside the transmitter through the cable gland.
    3. Tighten the cable gland: refer to the instructions of the glands used in your application for maximum tightness.
    4. If your installation does not require using both lead-throughs, plug the unused lead-through with an Ex compliant seal.
  2. Connect the screw terminal wiring as required in your application. For protected installation wiring diagrams, see Wiring with galvanic isolators and Wiring with Zener barriers.
    1. Open the cable fastening clamps below the screw terminals and lead the cables to the terminals through the clamps.
    2. Connect the wires to the screw terminals: for an example, see Figure 1.
      Note that Channel 1 (CH1) must always be wired. The transmitter receives power through the CH1 screw terminals, and does not power on if only Channel 2 (CH2) is wired.
    3. Adjust the length of the wires and close the cable fastening clamps so that they hold the cables in place.