Datasheet
"!# !
last update
November 30, 2010
reference
smtutin
page
26/27
8.7 Mode 15. Potm: 3 potentiometers, 1kΩ
ΩΩ
Ω-25kΩ
ΩΩ
Ω
In this mode, 3 potentiometers in the range of 1 kΩ to 50 kΩ can be measured. The connection of
potentiometers is depicted in
Figure 16
. When only a single potentiometer is measured with its slide
connected to, for instance, node B, nodes C and D should be connected to F. The voltage across the
potentiometers is a square wave with amplitude
V
DD
and frequency 1/4 of the internal oscillator frequency.
Figure 16. Connection of potentiometers to the UTI
It is not possible to compensate for the effect of lead wires in this mode. Therefore, the use of low-ohmic
potentiometers should be avoided. The measured voltages during each phase are indicated in
Table 28
and the specifications in
Table 29.
The relative position
M
for each potentiometer is given by:
M
T T
T T
y
y y
phase phase
phase phase
=
−
−
=
+
3 4 5 1
2 1
2
1 2
, ,
(7)
Phase Measured
voltages
Output periods
1 V
offset
Toffset=N*K
2
*Voffset
2 V
ef
+V
offset
Tef= N*K
2
*(Vef+Voffset)
3 Vcf+V
offset
Tcf=N*K
2
*(Vcf+Voffset)
4 V
bf
+V
offset
Tbf= N*K
2
*(Vbf+Voffset)
5 Vdf+V
offset
Tdf= N*K
2
*(Vdf+Voffset)
Table 28. Measured voltages during the measuring Pot
meters
Parameter (V
DD
= 5 V) Typical value
K
2
56 s/V
V
0
5 V
Potentiometer resistance 250-10k
Bridge output Voltage <+/- 12,5 mV
Accuracy Vcd/Vea 10 E-3
Resolution (SF=0) 14 bits
Table 29. Specifications of the Potm mode
E
C
D
B
A
F
/
,
/
0