Da Vinci 1.0a replacement for bed thermistor

2018/03/08 update still working great, no readjusting

I found a working replacement for the heated bed thermistor. It reads 300k cold 18c
The first test was 3 , 100k thermistors in series the bed ran about 110c-122c while printing.
The second test was 4 , 100k thermistors in series the bed ran 75c-85c while printing.
The last test was to have 3, 100k thermistors in series and also a 100k trim pot in series.
While printing slowly adjusting it so that while printing to get a stable 88c