> For the complete documentation index, see [llms.txt](https://docs.lorric.com/qr/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.lorric.com/qr/fu-tx310-ultrasonic-flowmeter-manual-en-v3/2-installation-method/2.1-power.md).

# 2.1 Power

If you do not purchase a LORRIC transformer, the instrument's applicable power supply should be 9-30 volts DC. The minimum current supply capability of the external power supply should be greater than 1 ampere. Current consumption will change with input voltage, but total power consumption is maintained at less than 2 watts. Please pay attention to positive and negative polarity when wiring. Please refer to the mark on the instrument case or wire according to the figure below. Incorrect polarity will cause the instrument to not operate and may damage it.

![](/files/-LvhShy_ZOfz_jvlgEop)


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