sets of +5Vdc regulator U101 and U104 (both are AN7805) to
produce two sets of +5Vdc regulated power sources. However,
these two sets of +5Vdc regulated power sources are not used
as +5Vdc power sources, they are used as two sets of +1.8Vdc
power sources by connecting their ground to the -3.1Vdc
output of Q102.
When being measured, higher level AC and DC voltage inputs
(except milli-volt signals) are properly attenuated by RN301
with automatically or manually selected voltage dividers to fit
into the input range of the A/D converter. There are a total of
five resistors inside RN301: a 10MΩ high resistance input
resistor and four selectable voltage dividing resistors: a
1.11MΩ, a 101kΩ, a 10kΩ and a 1kΩ resistor. Each of the four
voltage dividing resistors can be selected to create a series
circuit with the 10MΩ input resistor to form a voltage dividing
circuit that creates one of four dividing ratios of 1/10, 1/100,
1/1000 and 1/10000.
To Next Page
Loading...
