PAXUSB00 datasheet(28/36 Pages) REDLION

28 / 36 page

Communication Format

Data is transferred from the meter through a serial communication channel.

In serial communications, the voltage is switched between a high and low level

at a predetermined rate (baud rate) using ASCII encoding. The receiving device

reads the voltage levels at the same intervals and then translates the switched

levels back to a character.

The voltage level conventions depend on the interface standard. The table

lists the voltage levels for each standard.

Data is transmitted one byte at a time with a variable idle period between

characters (0 to ∞). Each ASCII character is “framed” with a beginning start bit,

an optional error detection parity bit and one or more ending stop bits. The data

format and baud rate must match that of other equipment in order for

communication to take place. The figures list the data formats employed by

the meter.

Start bit and Data bits

Data transmission always begins with the start bit. The start bit signals the

receiving device to prepare for reception of data. One bit period later, the least

significant bit of the ASCII encoded character is transmitted, followed by the

remaining data bits. The receiving device then reads each bit position as they are

transmitted. Since the sending and receiving devices operate at the same

transmission speed (baud rate), the data is read without timing errors.

Parity bit

After the data bits, the parity bit is sent. The transmitter sets the parity bit to

a zero or a one, so that the total number of ones contained in the transmission

(including the parity bit) is either even or odd. This bit is used by the receiver

to detect errors that may occur to an odd number of bits in the transmission.

However, a single parity bit cannot detect errors that may occur to an even

number of bits. Given this limitation, the parity bit is often ignored by the

receiving device. The PAX meter ignores the parity bit of incoming data and

sets the parity bit to odd, even or none (mark parity) for outgoing data.

Stop bit

The last character transmitted is the stop bit. The stop bit provides a single bit

period pause to allow the receiver to prepare to re-synchronize to the start of a

new transmission (start bit of next byte). The receiver then continuously looks

for the occurrence of the start bit.

IDLE 0 b01

bb3 b4 b56

1 IDLE

IDLE

IDLE 0

bb4 b5 b6 P1

IDLE

IDLE 0

b56 11

(7 data, no parity, 2 stop)

(7 data, parity, 1 stop)

(8 data, no parity, 1 stop)

Start bit

Stop bit

Note: b - b is ASCII data.

Character Frame Figure

LOGIC

RS232*

RS485*

INTERFACE STATE

TXD,RXD; -3 to -15 V

a-b < -200 mV

mark (idle)

TXD,RXD; +3 to +15 V

a-b > +200 mV

space (active)

* Voltage levels at the Receiver

8-Out

ASIN

Analog

Type

tYPE

AN-LO

AN-HI

udt

Analog

Update Time

PAR

Analog

Assignment

Analog Low

Scale Value

Analog High

Scale Value

Pro

Burn-out

Action

burn

PAXT

ONLY

6.8 mOdUle 8 - analOg OUTpUT parameTers () Ñ

PARAMETER MENU

Enter the analog output type. For 0-20 mA or 4-20 mA

use terminals 18 and 19. For 0-10 V use terminals 16 and

17. Only one range can be used at a time.

















ANALOG TYPE

ANALOG ASSIGNMENT







SELECTION

0 to 10 V

4 to 20 mA

0 to 20 mA

RANGE









Enter the Display Value that corresponds to 0 mA (0-20

mA) , 4 mA (4-20 mA) or 0 VDC (0-10 VDC).









ANALOG LOW SCALE VALUE

























ANALOG HIGH SCALE VALUE

ANALOG UPDATE TIME

PROBE BURN-OUT ACTION (PAXT ONLY)



to 



to 



to 





Enter the source for the analog output to retransmit:



= Display Input Value



= Maximum Display Input Value



= Minimum Display Input Value



= Totalize Display Value

Enter the Display Value that corresponds to 20 mA (0-20

mA) , 20 mA (4-20 mA) or 10 VDC (0-10 VDC).

Enter the analog output update rate in seconds. A value

of 0.0 allows the meter to update the analog output at a

rate of 20/sec.

Enter the probe burn-out action. In the event of a

temperature probe failure, the analog output can be

programmed for low or high scale.

- An analog output card must be installed in order to access this

module.

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