长周期大地电磁测深需要观测最长周期为几万秒的大地电磁场信号，这要求用于测量电场信号的不极化电极具有很小的极差，以及至少长达1—2个月的稳定时间,普通的不极化电极不能满足要求。通过改进电极电解质配方和电极结构，试制出铅氯化铅不极化电极。测量结果表明，该电极具有极差小、稳定时间长、使用寿命长、维护简单等优良特性。在山东菏泽等地的野外实验表明，该类不极化电极能够很好地观测几万秒的长周期信号。同等条件下，其性能优于国外同类产品，达到预期目标。

The longperiod magnetotelluric sounding need to observe magnetotelluric signals which the longest period is tens of thousands seconds. This requires that the nonpolarizable electrodes used to measure the electric signals should have a weak electrode potential and is stable for 1 to 2 months at least. The common nonpolarizable electrodes can not meet the requirements. By improving the electrolyte recipe and structure of electrode, the measurement results of the tried electrodes show that the electrodes have a weak potential, longtime stability, long service life, easy maintenance and other excellent properties. The practical application in Heze of Shandong Province and other places show that this type of nonpolarizable electrodes can be adapt for observing longperiod signal and be superior to similar foreign electrodes in the same conditions. So the experiment achieves the expected goal.