The effect of humidity on the d.c. resistance of an SnO2:Sb:SnCl2 thic
k-film planar resistor on an alumina substrate is reported. The films
of SnO2 are obtained using standard screen-printing technology. The th
ick-film paste is formulated by loading the SnO2:Sb system with varyin
g percentages of SnCl(2)2H(2)O. An increasing percentage of SnCl2 in t
he SnO2:Sb system increases the sensitivity to humidity and decreases
the initial resistance. A two orders of magnitude change in d.c. resis
tance is observed for a relative humidity change from 30 to 90%. A sma
ll hysteresis (3-10%) is observed. The response time is a few seconds
(6-8), though the recovery time is slow (8-10 min).