Measuring Mode - Beckhoff EL3692 Documentation

Commissioning
The default state of the EL3692 is 4-wire mode. In this mode the measuring current flows via terminal points
1(5) through the resistance to terminal point 3(7). The voltage measurement takes place via terminal points
2(6) and 4(8).
5.5.6

Measuring mode

The terminal supports 4 measuring modes. The measuring mode is selected via the Mode entries in the
process data (control word) or in CoE 0x80n0:0D [} 133]. The measuring mode determines the time of the
measurement and the wire connection.
• 0: 4-wire measurement
• 1: 4-wire measurement (single-shot mode)
• 2: 2-wire measurement
• 3: 2-wire measurement (single-shot mode)
Measurements
Measurements cannot take place simultaneously on both channels. 4-wire connection is
recommended for the EL3692.
Note
Operating mode Mode entry
Alternating mode Both channels measuring mode "0" or "2"
Single shot mode Both channels measuring mode "1" or "3"
Mixed mode One channel measuring mode "0" or "2", the other
channel mode "1" or "3"
Table 1: Operating modes
Alternating mode
This mode is the delivery state of the terminal. Both channels alternately measure a resistance at their
connection points. The measurement is indicated by the lit status LED.
Single shot mode
Each channel only measures on request by the application. A rising edge in the "Start Conversion" bit in the
control word triggers a measurement. If both channels are triggered simultaneously, the channels are
processed sequentially. The first channel has priority.
This mode is suitable for measurements during which heating of the test specimen due to repeated
measurements is undesirable.
Mixed mode
One channel measures continuously, the other only on request. This mode is a combination of the two
previous modes. Once channel measures continuously and interrupts its measurement only if a
measurement is requested on the other channel.
This mode is suitable for measuring high-resistance test specimens. Constant current flow (provided the
other channel is never activated) means that all charging processes are complete. A delay after CoE
0x80n0:31 [} 133] is therefore not required.
108 Version: 2.1
Principle of operation
EL3692