Olpas Tentacle sensors are equipped with a four core wire:
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Power (5.5-25V, ~0.8W)
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Ground
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RS485A
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RS485B
Connecting multiple sensors in a string, i.e. daisy chaining of sensors, is possible. The following requirements need to be met:
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The datalogger or power supply needs to supply sufficient power for all sensors to power on simultaneously. Use 1.5W as power per sensor to account for power on peak load.
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The modbus address of every sensor needs to be configured different
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Keep in mind the stub length, i.e. the cable length from sensor to the main data cable. Long stubs will lead to loss of signal integrity.
Olpas advises to keep stubs as short as possible (< 30cm, <50cm) with max. 5-10 sensors per chain. Olpas Tentacle sensors can be ordered with RS485 120ohm termination - make sure a RS485 terminated sensor is used at the end of the daisy chain. For multiple sensors it is recommended to use a higher power supply voltage (12V - 24V) to limit voltage drop in the line.