am452 AME, Inc., am452 Datasheet - Page 16

• Manufacturer Part Number: am452
• Description: Voltage-to-current Transducer Ic With A Differential Input - Analog Microelectronics
• Manufacturer: AME, Inc.

Here, G
amplifier (OP1). I
pin and which can raise the output current of the VI/ converter by a constant value.
1) Example 1: V
For a measuring bridge with a signal of V
the external components should be dimensioned in such a way that output current I
4...20mA.
If the input signal offset is negligible, resistors R
With the two voltage dividers it is sufficient to calculate just one of the two resistors; the other
can be selected within the stipulations given by the boundary conditions. In this example a
value of 5V has been selected for VREF, with 10k chosen for R
current of 20mA the voltage should drop by a typical value of 540mV at resistor R
following is accrued:
With reference to Equations (11) and (12) and the values given in Example 1 the following is
obtained:
By solving the above system of equations and taking the given defaults into account, the
following values are computed for the 3-wire, 4–20mA current interface:
R
R
R
If the offset output current is not exactly 4mA due to component tolerances and deviates from
this value, the voltage can be adjusted at pin 16 (SET) using voltage divider R
Figure 7) and the output value thus corrected (c.f.: Offset compensation using a voltage
divider at SET).
0
3
L
Analog Microelectronics GmbH
An der Fahrt 13, D – 55124 Mainz
= 27
= 110.74k
= 0...600
AM452 – Voltage-to-current transducer IC
I
is the overall gain of the instrumentation amplifier (IA) and the back-end operational
IN
SET
= 0...100mV differential, I
R
R
C
is the additional offset current which is set using a voltage at the SET
1
4
1
. 0
. 0
R
= 59.12k
= 5k
= 2.2µF
with a differential input
02
004
0
A
. 0
A
02
0
A
1 .
2
5
V
V
R
. 0
0
5
54
8
(
1 (
V
R
R
R
R
3
0
5
2
5
IN
10
k
= 10k
= 39
5
R
= 0...100mV (without an offset) at the IA input
k
k
1
OUT
)
)
0
= 4...20mA (3-wire)
, R
2
1
, R
5
V
R
0
2
, R
Phone: [phone]
Fax:
Internet:
Email: [e-mail]
February 2008 - Rev 1.2 - Page 16/21
(
R
3
3
5
and R
k
5
2
+49 (0)6131/91 073-30
k
http://www.analogmicro.de
and 5k for R
4
)
must be determined.
3
and R
4
. With a
0
OUT
4
. The
(13)
(see
is