User Manual

Page 51
EA Elektro-Automatik GmbH
Helmholtzstr. 31-33 • 41747 Viersen
Germany
Fon: +49 2162 / 3785-0
Fax: +49 2162 / 16230
www.elektroautomatik.de
[e-mail]
ELR 9000 Series
3.4.4.4 Simplied diagram of the pins
+
Digital Input (DI)
The internal circuit requires that a switch
with low resistance should be used (relay,
switch, circuit breaker etc.) in order to
send a clean signal to the DGND.
A digital output from a circuit or PLC may
not be sufcient if not an “open collector”.
V~0.5
AGND
Analog Input (AI)
High resistance input (impedance
>40k....100kΩ) for an OA circuit.
10k
12V
+
Digital Output (DO)
A quasi open collector, realised as high
resistance pull-up against the internal sup-
ply. In condition LOW it can carry no load,
merely switch, as shown in the diagram
with a relay as example.
V~2
AGND
Analog Output (AO)
Output from an OA circuit, only mini-
mally impedant. See specications
table above.
3.4.4.5 Application examples
a) Switching off the input via the pin “Rem-SB”
The pin Rem-SB can be used in remote control to switch the input on and off. It is recom-
mended that a low resistance contact such as a switch, relay or transistor is used to switch
the pin to ground (DGND).
A digital output, e.g. from a PLC, may be unable to cleanly effect this as
it may not be of low enough resistance. Check the specication of the
controlling application. See also 3.4.4.4 above.
b) Remote control of current and power.
Requires remote control to be activated (Pin “Remote” = LOW)
The set values PSEL and CSEL are generated from, for example, the
reference voltage VREF using potentiometers for each. Hence the
electronic load can selectively work in current limiting or power limit-
ing mode. According to the specication of max. 5mA for the VREF
output, potentiometers of at least 10kΩ must be used.
The voltage set value VSEL is permanently assigned to AGND
(ground) and therefore has no inuence on constant current or power
operation.
If the control voltage is fed in from an external source it is necessary
to consider the input voltage ranges for set values (0...5V or 0...10V).
Use of the input voltage range 0...5V for 0...100%
set value halves the effective resolution.
Example with external
voltage source
Example with
potentiometers
c) Reading actual values
Via the AI the input values of current and voltage can be monitored. These can be
read using a standard multimeter or similar.