Potential gradient is measured using a JCI Chilworth 131F adverse conditions field meter. It is mounted on a 2 m pole buried in the ground within the Langford Apiary.

The field mill is ~ 5 m from any other object. Site includes wind breaks nearby (< 2 m height) to protect beehives and some trees which may affect measurements. The instrument is located 23 m a.s.l.

Linear response and calibration for the instrument was tested on manufacture at Chilworth Technology in 2016.

Measurement frequency is 10Hz.

This is used in the Glocaem potential gradient network