Yokogawa EJA440E User Manual download pdf (Page 22)

<3. Operation>

3-14

IM 01C25T03-01E

Note that changing the upper range value does not

cause the lower range value to change but does

change the span.

• Example 2: When the upper range value is to

be changed to 10 kPa with the

present setting of 0 to 30 kPa, take

the following action with an input

pressure of 10 kPa applied.

FEED NO OK

SET

H11:AUTO URV

10.000 kPa

DATA DIAG PRNT ESC

PARAM

H10:AUTO P LRV

0 kPa

H11:AUTO P URV

10.000 kPa

H20:AUTO SP LRV

0.0 MPa

ESC

SET

H11:AUTO P URV

30 kPa

+ 30

The lower range value is not

changed, so the span changes.

Parameter C22 is changed at the

same time.

Press the key twice.

The upper range value is

changed to 10 kPa.

Press the (OK) key.

F0335.ai

(15) Sensor Trim

Each transmitter is factory characterized. Factory

characterization is the process of comparing a

known pressure input with the output of each

transmitter sensor module over the entire pressure

and temperature operating range. During the

characterization process, this comparison

information is stored in the transmitter EEPROM. In

operation, the transmitter uses this factory-stored

curve to produce a process variable output (PV), in

engineering units, dependent on the pressure input.

The sensor trim procedure allows you to adjust

for local conditions, changing how the transmitter

calculates process variables. There are two ways

to trim the sensor: a zero trim and a full sensor trim.

A zero trim is a one-point adjustment typically used

to compensate for mounting position effects or

zero shifts caused by static pressure. A full sensor

trim is a two-point process, in which two accurate

end-point pressures are applied (equal to or greater

than the range values), and all output is linearized

between them.

a. Zero Trim (J11: P ZERO ADJ, J15: P ZERO

DEV, J55: EXT ZERO ADJ)

The transmitter supports several adjustment

methods. Select the method best suited for the

conditions of your application.

Adjustment

Method

Description

Using the BT200 Set the present input to 0%.

Adjust for 0% output at input level

of 0%.

Adjust output to the reference

value obtained using other means.

If the input level cannot easily

be made 0% (because of tank

level, etc.), adjust output to the

reference value obtained using

other means, such as a sight

glass.

Using the

external zero-

adjustment

screw

Adjust zero point using the zero-

adjustment screw on the transmitter.

This permits zero adjustment without

using the BT200. Accurately adjust

the output current to 4 mA DC or

other target output value using an

ammeter that accurately reads output

currents.

When using BT200, the output signal can be

adjusted either in % or pressure unit. The unit

can be selected by the parameter J09: ADJ UNIT.

Output signal can be changed by displaying

parameter A10: OUTPUT for % or J10: OUTPUT

for pressure unit.

This section discribes the zero adjustment

procedure by using the pressure unit.

a-1. Zeroing

Setting the parameter J11: P ZERO ADJ carries

out the zero adjustment and automatically sets the

applied “0” input values to the transmitter’s output

value of zero, keeping the span constant. Use this

setting when the LRV is known to be 0 kPa.

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