OK, I figured it out. My mistake, to set the end piece extension, two actions are required. 1. Set the end piece zero offset using the FUNC button. 2. Toggle the 'back' reference from 'back of case' to 'back of end piece offset', using REF + FUNC (hold 2 seconds) The new distoX2 now works as expected, although I still need to calibrate it. This IS mentioned in the user manual. Bruce From: Therion <therion-bounces@speleo.sk> On Behalf Of Bruce Mutton via Therion Sent: Sunday, 28 October 2018 10:19 To: 'List for Therion users' <therion@speleo.sk> Cc: Bruce Mutton <bruce@tomo.co.nz> Subject: [Therion] DistoX2 zero distance reference points and end piece extension I have an older distoX2 and a new distoX2, and came to thinking about building a protective case. Naturally the topics of zero reference points and end piece extensions has come to mind. Rather belatedly I thought I would run a rudimentary test over a short ~250mm distance that I could measure with a steel ruler, just to check my understanding of the behaviour. It was not as I expected, and I have not found an explanation in any of the documentation. Maybe someone has similar experiences. The newer distoX2 is not yet calibrated, and they both have differing hardware and firmware versions, so either or both may be the cause of the differences. Perhaps a table is the best way to document what I have found. Disto Old New Hardware 1.0 1.1 Firmware 2.4 2.5 ID 2973 4036 End piece setting 0.012 m 0.060 m Reference toggle cycle End piece-front-tripod Back-front-tripod Comment End piece extension reference option is available End piece extension reference option is NOT available End piece disto - ruler comparison 267 - 265 mm works as expected N/A Back disto - ruler comparison N/A 253 - 312 mm end piece setting ignored, does not work as expected Front disto - ruler comparison 132 - 131 mm 131 - 131 mm Tripod disto - ruler comparison 245 - 243 mm 244 - 243 mm Calibrated Yes Not yet Apparent accuracy 1-2 mm 1 mm except with end piece One explanation could be that the end piece zero reference is not available and any end piece setting will be ignored until the distoX2 has been calibrated. I am hoping that is what the situation is, and it will be easy enough to test, once I get around to it. It does seem a bit odd however, as I assume the calibration is all about directions, and not distances. Thoughts? Bruce