Doing a test with my 1730 for NAPIT inspection. Meter came up with CON which means connection problem. Thought that meter was playing up. Polarity was correct and the Ze was 83 ohms. Got City's to send out a brand new inbox 1730 did the same test with the same result CON. Can't be two meters with same problem. Inspector had his 1530 and plugged in exactly the same and up came the zs reading straight away. spoke to megger and they had no solution and tried to replicate at their work shop, said would et back but has not, good after service .An ideas