ELECTRONICS AND INTERFACING
VOLTAGE DIVIDERS
If you wish to measure a signal which varies over a range greater than the input range
of a digital input, a voltage divider can drop the voltage of the input signal to the level
the digital input can measure.
A voltage divider takes advantage of Ohm's law, which states,
Voltage = Current * Resistance
and Kirkoff's voltage law which states,
The sum of the voltage drops around a circuit will be equal to the voltage drop for the
entire circuit.
Implied in the above is that any variation in the voltage drop for the circuit as a whole
will have a proportional variation in all the voltage drops in the circuit.
15
SIGNAL HIGH
SIGNAL LOW
R1
R2
A/D BOARD
HIGH INPUT
A/D BOARD
LOW INPUT
SIGNAL
VOLTS
V1
V2
Vout
Vin
=
R1 + R2
R2
Vin
Vout
SIMPLE VOLTAGE DIVIDER
DETAILED INSTALLATION
We highly recommend that you use the InstaCAL procedure described in the previous
chapter to guide you through setting up your board. However, the following sections
are provided in case you need to set up your board and you do not have access to the
InstaCAL program.
The CIO-CTR has one bank of switches, a base address switch, and one jumper block
which must be set before installing the board in your computer. The calibration and
test program included with the CIO-CTR will show how these switches are to be set
and should be run before you open your computer.
BASE ADDRESS
Unless there is already a board in your
system which uses address 300 HEX
(768 Decimal) then you can leave the
switches as they are set at the factory.
In the example shown here, the CIO-
CTR is set for base address 300H (768
Decimal).
Certain address are used by the PC, others are free and may be used by the CIO-CTR
and other expansion boards. We recommend BASE = 300H (768D) be tried first.
MDA
3B0-3BB
HARD DISK (AT)
1F0-1FF
SDLC
3A0-3AF
80287 NUMERIC CO-P
(AT)
0F0-0FF
SDLC
380-38F
8237 #2 (AT)
0C0-0DF
PARALLEL PRINTER
378-37F
NMI MASK (XT)
0A0-0AF
HARD DISK (XT)
320-32F
8259 PIC #2
0A0-0A1
PROTOTYPE CARD
310-31F
DMA PAGE REGISTERS
080-08F
PROTOTYPE CARD
300-30F
CMOS RAM & NMI
MASK (AT)
070-071
SERIAL PORT
2F8-2FF
8742 CONTROLLER (AT)
060-064
SERIAL PORT
2E8-2EF
8255 PPI (XT)
060-063
GPIB (AT)
2E0-2E7
8253 TIMER
040-043
EGA
2D0-2DF
8259 PIC #1
020-021
EGA
2C0-2CF
8237 DMA #1
000-00F
FUNCTION
HEX
RANGE
FUNCTION
HEX
RANGE
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