pa4tim@gmail.com writes: I have 4 weston cells in a guildline cabinet with oven. I have the cal data for the first 10 years they have been used. After this time the oven was turned off , the lab was closed but all gear stayed put on that same place over 30 years (the lab was turned into a server room but all the gear just stayed unused ) I made a graph from the data. Took a ruler and extended the lines. After a few months I had a change to measure them with a calibrated 6,5 digit meter and a year later a 7,5 digit meter and the values I found where plus/min a few uV on the lines. But more important the difference between the individual cells was spot on with my graph. I have that same unit myself. For some years I kept it on and would periodically compare the cells to my (calibrated) Datron 4910's. I kept logs of the voltage sampled weekly using an 8.5 digit meter for differential comparison for 2 or 3 years. I was surprised at how stable and predictable they were. But, I stopped doing that probably 5 years ago. Nostalgia strikes, I'll plug it back in and see what's changed. Unfortunately, it takes weeks for the voltage to stabilize from a cold start. -- Bill Ezell ---- They said 'Windows or better' so I used Linux.