Remote-processing RPC-52 Manuale Utente Scaricare il pdf (Pagina 28)

ANALOG I/O CHAPTER 10

Page 26

Figure 10-1 Analog I/O

DESCRIPTION

The RPC-52 has 8 single ended analog input channels.

These channels can be used to measure voltages from

transducers, 4-20ma current loops, thermistors, etc.

Input voltage range is 0 to 5 volts with 10 bit (1024

count) resolution. In addition to the inputs, there are 2

analog outputs that are shared with the PW M positions.

These outputs may be used to control the speed of

motors or provide an analog indication of a level or

position. Output voltage can be varied in 255 steps from

0 to 5 volts.

This chapter begins with basic information on connecting

and using analog inputs. Later, descriptions of how to

measure voltages other than 0 to 5 volts, data logging,

and calibration are explained. Generating analog outputs

are then discussed.

The analog inputs on this card are above any others used

in the opto module slots. Inputs and outputs discussed

here are not optically isolated.

CONNECTING ANALOG I/O

All analog I/O interfaces through connector J1. An

STB-20 and CM A-20-24 ribbon ca ble can be use d to

provide screw terminal interface. Screw termina ls

accommodate 12-22 gauge wiring.

Additional components, such as r esistors and capacitors,

may be connected directed to the scre w term inals.

Analog I/O J1 pin out

Use the following table to connect to the appropr iate

input or output. Pin numbers correspond to those on the

STB-20.

Description J1 pin

Channel 0 in 1

Analog ground 2

Channel 1 in 3

Analog ground 4

Channel 2 in 5

Analog ground 6

Channel 3 in 7

Analog ground 8

Channel 4 in 9

Analog ground 10

Channel 5 in 11

Analog ground 12

Channel 6 in 13

Analog ground 14

Channel 7 in 15

Analog ground 16

Analog 0 out 17

Digital ground 18

Analog 1 out 19

Digital ground 20

Grounding

Analog ground is somewhat isolated from digital ground.

While the ground plane is connected between the two,

analog ground is a virtual "island" connected only in one

place to digital ground. To minimize noise pickup, the

sending device should be connected to analog ground.

When both analog and digital grounds come from the

same device, you will have to play around with the

grounds to determine which scheme provides the best

performance for your system.

ACQUIRING ANALOG DATA

Analog data is accessed with the AIN function. The

syntax is:

A = AIN(channel)

This function assigns the analog value of a channel to the

variable; A in th is case. The value returned is alway s in

the 0 to 1023 range because the converter is 10 bits. A 0

corresponds to 0.000V and 1023 corresponds to 4.99V.

To view the result of a conversion in the command

mode, type:

print ain(0)

The result at channel 0 is returned.

The AIN function requires about 1 ms to convert the

data. Additional time is needed to store the data. The

example below takes 255 data samples and stores them

into an array which requires 6 bytes per entry. The

second example takes only two byes per entry, can save

to extended m emor y, but requir es a longer time to get a

1 2 ... 23 24 25 26 27 28 29 30 31 32 33 34 35 36

Commenti su questo manuale

Nessun commento

Remote-processing RPC-52 Manuale Utente Pagina 28

Commenti su questo manuale

Prodotti e manuali riguardandi Computer Remote-processing RPC-52