Sensors

The HyDip Tank Gauging device can use any 24V, 4-20mA linear response level sensor. Here we describe how to connect three common types.

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The HyDip controller is not EX rated and must not be installed within a hazardous zone.

Only use sensors rated for use in hazardous environments inside a hazardous zone.
A certified hazardous area electrician MUST inspect all devices and review the installation to certify that the installation complies with local regulatory standards for flammable or hazardous environments.

Hydrostatic pressure gauge sensor

Frequently in diesel tank applications you may install a 0m to 3m hydrostatic pressure gauge with a cable insulation rated for submersion in petroleum fuels.

The hydrostatic sensor is lowered to the bottom of the tank and measures the hydrostatic pressure of the fluid above the gauge. Hydrostatic gauges provide a measurement of the fluid height above the gauge. This measurement is directly converted into litres for the specific dimensions of the tank as set up in the HyDip device configuration online.

Cabling

At the free end of the hydrostatic gauge cable you should find:

  • Two signal wires, one positive and one negative.
  • A ground wire made from the shielding on the cable.
  • A vent tube, which should be left unobstructed and exposed to atmospheric pressure. If this vent tube becomes blocked, or is subjected to fluid entry, the accuracy of the gauge measurement will be affected.

Take care to ensure that:

  • The breathable filter cap normally supplied by the gauge manufacturer is inserted at the end of the vent tube to protect it from dust ingress.
  • When shortening the cable length, use a sharp knife to cut the vent tube to ensure it does not get pinched or crushed.

Please refer to the sensor manufacturer’s documentation for detailed specifications and installation instructions.

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Pressure sensors have limits

Do not exceed the maximum pressure or depth rating for the pressure sensor as this may cause permanent damage to the gauge

Connecting the hydrostatic gauge to HyDip

  1. Identify the two signal wires, and connect them, taking care to get the correct polarity, to a green 2-pin terminal block connector plug using the screw fittings.
  2. If the cable supplied with the gauge is not long enough, install a weather proof junction box to connect the extra cable length. Cap the vent tube with its filter within the junction box. Normally there will be enough venting through the conduit glands to keep the vent tube at atmospheric pressure. Ensure all cable conduits are water tight to prevent external water entry into the junction box. If you are using a vented junction box make sure there is no possibility of water entry.
  3. Plug the 2-pin green terminal block into the socket on the HyDip Tank Gauging device (TK1 for sensor 1, TK2 for sensor 2 and so on). Note that:
  • The plugs will only fit the sockets one way up
  • The negative polarity of the gauge must be connected to TK1- on the HyDip side panel, and the positive polarity to TK1+. You should identify the correct wire polarity by referring to the wire colour coding specified in gauge manufacturer’s data sheet.

Ultrasonic sensors / radar sensors

Ultrasonic or radar devices are available in screw or flanged fittings and attach to the top of a tank.

These devices transmit a signal pulse which is reflected back from the fluid surface to give a measurement of the distance to the liquid level. This measurement is converted into litres for the specific dimensions of the tank as set up in the HyDip device configuration.

Connecting the ultrasonic or radar gauge to HyDip:

  1. Remove the cover of the ultrasonic or radar sensor, and locate the connectors labelled 4…20mA. They should be labelled positive and negative. Insert a two-wire cable through the access port and attach it to these terminals.
  2. Connect the other end of the wire to a green 2-pin terminal block plug using the screw fittings.
  • Ensure the sensors are installed with the correct polarity; the plugs will only fit the sockets one way up.
  1. With the wires attached, simply plug the green terminal block plug into the appropriate socket on the HyDip (marked TK1 for sensor 1, TK2 for sensor 2 and so on).
  2. Take great care that the negative polarity of the gauge is connected to TK1- on the HyDip side panel, and the positive polarity to TK1+.

Please refer to the sensor manufacturer’s documentation for detailed specifications and installation instructions.

For EX rated sensors the connection may be slightly different, e.g. access may be gained by routing the wires through a side port. Refer to the gauge manufacturer’s documentation for detailed installation instructions.

Magnetostrictive sensors

Another sensor you may use is a magnetostrictive liquid level sensor which uses a pole and float system to modify an electric signal.

The length of the rigid pole should be the same as the depth of the liquid. A float containing a magnet rests on the surface of a given liquid, and is able to slide up and down the pole as the liquid level changes. The position of the float on the pole in mm is converted into litres for the specific dimensions of the tank as set up in the HyDip device configuration.

At the free end of the magnetostrictive gauge cable you should find:

  • Two signal wires, one positive and one negative.
  • A ground wire made from the shielding on the cable.

Please refer to the sensor manufacturer’s documentation for detailed specifications and installation instructions.

Connecting a magnetostrictive gauge to HyDip

  1. Identify the two signal wires, and connect them, taking care to get the correct polarity, to a green 2-pin terminal block connector plug using the screw fittings.
  2. If the cable supplied with the gauge is not long enough, install a weather proof junction box to connect the extra cable length. Ensure all cable conduits are water tight to prevent external water entry into the junction box. If you are using a vented junction box make sure there is no possibility of water entry.
  3. Plug the 2-pin green terminal block into the socket on the HyDip Tank Gauging device (TK1 for sensor 1, TK2 for sensor 2 and so on).