Pressac CT Clamp

Compatibility

Compatible with EpiSensor Edge over LoRaWAN.

Register it on your LoRaWAN network server with its DevEUI and keys. Edge, on the Gateway, reads its decoded uplinks from that server.

Edge reads 4 values from it, listed under Interface.

Connect it with

• 
  Gateway ZGW-20
  From €899 ex VAT Configure Gateway

Specifications

Pressac’s CT Clamp for LoRaWAN clips around a conductor and measures its AC current at 50 or 60 Hz. The three-channel version takes three clamps, one per conductor, into one transmitter; the single-channel version takes one. Clamps come in 60 A, 200 A and, on the three-channel version, 600 A sizes, for conductors up to 10, 24 and 36 mm across.^1, 2

Power

Self-powered from the measured supply. Energy harvested from the measured conductor; no battery and no supply wiring. It needs at least 1.25 A in the conductor to run, and 1.5 A for 30-second reporting.¹

Measurement ranges

0 to 60 A (±0.1 A and 2 %), 0 to 200 A (±0.2 A and 2 %), 0 to 600 A (±0.5 A and 2 %, three-channel only)¹

Channels

1 or 3, one clamp per channel¹

AC frequency

50 Hz or 60 Hz¹

Sampling frequency

22.6 kHz¹

Reporting

Average of 5 readings every 30 s from 1.5 A; average of 75 readings every 15 min from 1.25 A¹

Conductor diameter

10 mm or less (60 A), 24 mm or less (200 A), 36 mm or less (600 A)¹

LoRaWAN

Version 1.0.4, Class A, OTAA¹

Frequency plans

EU868, US915; +14 dBm transmit power, -146 dBm sensitivity¹

Transmitter

Nylon 66, IP4X, about 80 × 55 × 20 mm, indoor¹

Operating conditions

-5 to 40 °C, 0 to 85 % RH¹

Part numbers

CTLW_1CH_XXA_XXXX (single channel), CTLW_3CH_XXA_XXXX (three channel)¹

Compliance

CE, RoHS, WEEE, FCC¹

Where it is used

• Circuit and machine monitoring in commercial and industrial buildings, where clamps go on without switching anything off.

  Transformer and distribution board monitoring

• Sub-metering by zone or tenant across many sites, where battery-free sensors avoid a battery round.

  Multi-site energy monitoring

• Plant that runs most of the time, such as air handling units and refrigeration, where 30-second current shows each start and stop.

  HVAC energy monitoring for commercial buildings

Interface

Device class

Class A³

Regional plans

EU868, US915

Activation

OTAA

LoRaWAN version

1.0.4

Default uplink interval

30 seconds from 1.5 A; 15 minutes from 1.25 A

Ports

Decoded fields

Readings and settings, with units and ranges where Pressac publishes them.³

The currents are signed 16-bit little-endian values in hundredths of an amp, and Pressac’s decoder reports their absolute value. The channel order in the bytes is not 1, 2, 3: bytes 1 and 2 hold channel 3, bytes 3 and 4 channel 1, and bytes 5 and 6 channel 2. Byte 7 is the number of 30-second periods averaged into the values.³

The counter goes above 1 when the device averages over longer periods, in low-power mode or when earlier uplinks were not sent, so a value of 30 means the currents are the average of the last 15 minutes.³

Setup

1. Register it on the network server

   Add the transmitter to the site’s LoRaWAN network server for OTAA on EU868 or US915, and load Pressac’s CT clamp decoder.³

2. Clip the clamps on

   Clip each clamp around a single conductor, not around a whole cable, within its size: 10 mm for the 60 A clamp, 24 mm for 200 A and 36 mm for 600 A. The supply stays on.¹

3. Mount the transmitter outside the panel

   Fix the transmitter outside the metal panel, where the radio can reach a gateway, with the clamp leads running inside.¹

4. Wait for load

   The transmitter starts once a clamped conductor carries 1.25 A. At 1.5 A and above, expect an uplink about every 30 seconds.¹

5. Check the channel order

   Compare each decoded channel with a clamp meter on the same conductor. Mapping the bytes by the decoder, not by position, avoids swapping channels 1 and 3.

Common questions

Why is the sensor not sending anything?

It powers itself from the measured current, so it needs at least 1.25 A in a clamped conductor to run and 1.5 A for 30-second reporting. A circuit that is off, or lightly loaded, gives it no power.¹

Does it measure energy?

It measures AC current only, as an average over each reporting period. Energy needs a voltage and power factor from elsewhere, or an assumed value.^1, 3

Does it need a battery or calibration?

Neither. The transmitter is battery-free and Pressac states that no calibration is needed.^1, 4