GEM610 engine monitor

I have no knowledge of the instrument, but do recall Dallas who used to make all sorts of weird devices, with batteries sealed into them. Some of the stuff even worked, most of the time. I recall doing a multizone temperature controller which used their DS1820 “one wire” temperature sensors. These each had a unique 64-bit ID, which was a great concept except that somebody still had to tell the instrument which sensor was located physically where. Often they mysteriously stopped working and one had to power cycle the whole thing.

I suspect GEM used the DS1494 because it gave them a battery backed CMOS RAM, a battery, a unique serial number, and a real time clock with which to time stamp the data log. It’s a typical fresh from college engineer’s way of doing it – without much though for what happens when the battery needs to be replaced, and without knowing that CMOS battery backed up RAM is notorious for getting corrupted by noise and spikes.

The very best battery life achievable is with a DS1302 RTC (which has been out since 1991) which draws about 200nA and a decent size lithium “coin” cell will last about 20 years. That is about the shelf life of the battery and plenty long enough for a pissed off customer to not go looking for your goolies, but for an avionics product it isn’t good enough. And the DS1494 is specified at 10 years which is even worse. My plane is basically “new” yet it is 12 years old!

Also the only proper way to store nonvolatile data for an industrial application is in EEPROM or FLASH. The only reason for using battery backed up CMOS RAM is if you need to write very fast and very often; neither is the case in an engine data logger.

Unless Maxim still make some replacement part, I think that unit is worthless.

I don’t think you will be able to do anything clever via the IRDA port. It is likely to be just a data download port. It may have an undocumented protocol on it for diagnostics and firmware upgrades (more likely to be so if there is no other data connector somewhere) and then yes you could in theory load different firmware in there, but how will you develop it without knowing the hardware details?

The DOS based laptop is just a device for reading out the data. It doesn’t mean the GEM box runs DOS – it almost certainly runs nothing like that. From that era, it may be a Z80 or similar, like the Shadin fuel totalisers.

If the clock does not work, what time stamps are on the engine logs?

I have found it very useful to be able to look at old engine logs around a specific date/time.

Don’t get me wrong – I used to program in assembler

You can put DOS5 or DOS6.2 onto just about any laptop which has an IDE-compatible HD controller. Most will be SATA, which DOS won’t recognise, but some of those can be switched (in the BIOS) to look like IDE. That config doesn’t always work, but it’s a start. I have 3.5" DOS 6.2 install diskettes somewhere if you need them…

The best software for downloading EDM700 data was under DOS. There have been loads of troubles with the windoze versions since, if you allowed the queue to wrap round. It is only a year or so ago they fixed it.

Is the gem602 the one from Insight Avionics?

In that case they have a great replacement … A G3 or G4

I’ve had an Insight 610 for years now, and with LOP becoming popular have been looking into trying to download data from it, so this post is pretty interesting.

Old HP palmtops like the 200LX are about $80 on eBay, but the Insight software (GEMCOM.EXE) is nowhere to be found on the internet.

Maxim has a USB interface that can be used to read their iButton devices for about $55 (I don’t know if it will work on the DS1494 since this is a discontinued part) I have one of these iButton USB interfaces, if I come across an old DS1494 I’ll let you know.

Google turns up this and contacting them might be productive.