B.2 Limiting And Operating Data Of The Rs232C Data Interface - Mettler Toledo AE Série Mode D'emploi

B.2 Limiting and operating data of the RS232C data interface

Transfer principie:
The transmit lines have the following characteristics:
These values are valid at a load resistance of at least 3 kΩ. The sources are set up so that they are protected against external
current sources up to 25 V / 0.5 A (of any polarity).
The maximum permissible current in such cases is 0. 5 A. With short-circuit to ground or to another line, the maximum
permissible current is also 0. 5 A. With a load resistance of a maximum of 7 kΩ, the voltage level at the output of the balance
does not exceed 15 volts.
Receiver lines: The input resistance of the circuit lies between 3 kΩ and 7 kΩ. The idle input voltage (bias) is not more than
2 V. The receive circuit is set up for voltages of at least 25 volts. The maximum capacitance of the receiver circuit and cable
does not exceed 2500 pF. Input voltages of -3 V and less are interpreted as MARKING / OFF (HIGH). Those of +3 V and more
are interpreted as SPACING / ON (LOW). The absolute values of the voltages must not exceed 25 V. Voltages between -3 V
and +3 V are not defined.
Handshake: If the "Data Terminal Ready" line indicates a voltage of ≥ + 3 V, the 012 data output transmits results. If the value
is ≤ -3 V, the data output will not transmit. If the level changes from positive to negative during a transmission, a maximum
of 2 characters will be sent. If the level changes back to positive, the transmission is continued.
If the line is not used, the data output operates in the same way as when the external instrument registers readiness.
6
– bit serial
– asynchronous
– one start and one stop bit
– voltage-controlled data interface
– 7 bits per character plus parity bit (ASCII)
– negative voltage in idle conditon
MARKING / OFF (HIGH):
SPACING / ON (LOW):
at least -3 Volt
at least +3 Volt