Videographic recorders

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Also See for SM2000:

- User manual (138 pages) ,
- User manual supplement (25 pages) ,
- Hardware installation (12 pages)

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Videographic Recorders

SM1000 and SM2000

2.9.6 Switch Functions – Figs. 2.9 and 2.10

The switch functions, HS (High Select), MS (Median Select) and

LS (Low Select) are used to select between the highest, median

and lowest of three analog values – see Fig. 2.9.

x

y

z

Fig. 2.9 High, Median and Low Select

The switch function Mux (Multiplexer) is used to switch between

2 analog values when a third value becomes true – see

Fig. 2.10.

x

y

s

Fig. 2.10 Multiplexer Operation

2.9.7 Absolute Value Function – Fig. 2.11

The Absolute Value Function converts any negative value to it's

positive equivalent – see Fig. 2.11.

Fig. 2.11 Absolute Value Function

IM/SM2000ADV Issue 7

Therefore, if the Absolute Value Function is used to monitor the

difference between two flows A and B, where Flow A could be

greater than or less than Flow B, the function will always return a

positive value, which represents the unsigned magnitude of the

difference between the flow rates.

2.10.1 Liquid Flow – Fig. 2.12

y

Liquid Flow is measured in two ways:

1. Using a linear flow device such as Vortex, Swirl,

Ultrasonic, Turbine and Magnetic Flowmeters

2. Using a differential pressure transmitter across an orifice

z

plate or wedge.

Corrections can be applied to compensate for variations in

x

temperature and density – see Fig. 2.12, page 16.

Square Root Extraction and Scaling

Normally, square root extraction and scaling (

achieved in the DP transmitter or using an input linearizer within

the recorder.

If this is not possible, a math block can be used as follows:

Temperature Compensation

Assuming linearization and scaling has been achieved on either

the DP transmitter or linearizer input, temperature compensation

can be calculated as follows:

Qc

=

This is implemented in the recorder (assuming the linearized flow

is on input a1) as follows:

Qc

=

This requires two math blocks:

m2

=

Q

-------------------------------- -

(

)a

1

+

t

–

t

r

b

a1

-------------------------------- -

×

t

–

t

a

+

1

r

b

×

t

t

a

1

and

m3

a1 m2

–

+

=

r

b

2 Math Configuration

Q

=

K h

) is

⁄

created as follows:

15

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