Transcript Document

+15 V, -15 V measured through R/3R voltage divider gives ~ 6.7 V, not 10 V as expected.
attributed to myDAQ-internal connections associated with grounds such as AGND.
to circumvent, use +15 V and nearby AGND to supply 15 V, rather than the 30 V orignally
desired.
as before, accuracy measurement can be performed using DMM channel, this time using
20 V scale. sample measurement reveals 14.90 +/- 0.09 V (compare to 30.0 +/- 0.4 V
from last lecture)
now, let’s measure the precision of the +15 V power supply:
a) for observations every 5 µs (200 kS/s)
b) for observations every 0.1 s
note: DMM is not fast enough for either (a) or (b), and even if it was, coarse resolution
on the DMM complicates evaluation of precision
 use R/2R voltage divider in conjunction with ai0
J=2
x_1 = V_PS
x_2 = V_ai0
r = V_measured = x_1 + x_2 = V_ai0 + V_PS
3-minute records
ai0 shorted
ai0 monitoring
15V through V divider
to myDAQ 1
to myDAQ 2
2.26 kΩ
to myDAQ 2
to myDAQ 1