This current sensor is a carrier board or breakout board for Broadcom’s ACHS-7121/7122/7123/7124/7125 Hall effect-based linear current sensors; we therefore recommend careful reading of the ACHS-7121/7122/7123 datasheet (1MB pdf) or ACHS-7124/7125 datasheet (1MB pdf) before using this product. The following list details some of the sensor’s key features:
Details for item #4034
The ACHS-7124 sensor operates at 5 V and is designed for bidirectional input current from -50 A to 50 A. When Vcc is 5 V, the output voltage is centered at 2.5 V and changes by 40 mV per amp of input current, with positive current increasing the output voltage and negative current decreasing the output voltage.
This board ships assembled with all surface mount components, and a 3×1 strip of 0.1″ header pins is included but not soldered in.
Note: This sensor should not be operated at sustained currents over 40 A without additional external cooling. In our tests, we found that with sufficient current path connections, the IC could tolerate 50 A for approximately two minutes before exceeding its maximum temperature rating of 150°C, and it could tolerate up to 40 A continuously. Therefore, unless you are taking special steps to keep the IC cool, we recommend limiting continuous currents to under 40 A. Even with a low conductive path resistance of 0.7 mΩ, the board can get hot enough to burn you when the current is in the tens of amps, and the IC does not feature any kind of over-temperature protection, so thermal issues should be taken into consideration for high currents.
Using the sensor
This sensor has five required connections: the input current (IP+ and IP-), logic power (VCC and GND), and the sensor output (OUT).
The sensor requires a supply voltage of 4.5 V to 5.5 V to be connected across the VCC and GND pads, which are labeled on the bottom silkscreen, and the sensor outputs an analog voltage that is linearly proportional to the input current.
The FILTER pin lets you adjust the board’s bandwidth by adding a capacitor, CF, to ground (a ground pad has been added next to the FILTER pin for convenience) in parallel with the 1 nF capacitor that is already on the board. Without any external filter capacitor, the bandwidth is 80 kHz. The datasheet provides more information on how the external filter capacitor affects bandwidth.
You can insert the board into your current path in a variety of ways. For low-current applications, you can solder 0.1″ male header pins to the board via the smallest pair of through-holes on the input-current side of the board. For higher-current applications, you can solder wires directly to the through-holes that best match your wires, or you can use solderless ring terminal connectors. The largest pair of through-holes are big enough for #6 screws.
Warning: This product is intended for use below 30 V. Working with higher voltages can be extremely dangerous and should only be attempted by qualified individuals with appropriate equipment and protective gear.
Schematic and dimension diagrams
Schematic diagram of the ACHS-712x Current Sensor Carrier.
The dimension diagram is available as a downloadable PDF (318k pdf).
|Size:||0.7" x 0.8"|
|Current sense||0.040 V/A1|
|Minimum logic voltage||4.5 V|
|Maximum logic voltage||5.5 V|
|Supply current||15 mA|
|Version||-50A to +50A|
|PCB dev codes||cs01b|
|Other PCB markings||0J12458, blank white box|
1. When Vcc is 5 V.
This DXF drawing shows the locations of all of the board’s holes. The through-hole sizes and locations in this file also apply to cs01b versions of the PCB, though some of the via locations are different.