+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 orignallydesired.

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 snote: 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 = 2x_1 = V_PSx_2 = V_ai0r = V_measured = x_1 + x_2 = V_ai0 + V_PS

3-minute records

ai0 shortedai0 monitoring

15V through V divider

to myDAQ 1

to myDAQ 1

to myDAQ 2

to myDAQ 2

2.26 kΩ