Ahlborn ALMEMO 2590-2A Operating Instructions Manual page 21

8. Connecting the sensors / transducers
isolation. The voltage at the measuring inputs themselves must not exceed 5
volts (between B, C, D, A and - ).
The power supply is isolated by the transformer in the mains adapter or by a
DC/DC converter in connecting cable ZA2690-UK. Data and trigger cables are
equipped with optocouplers. If analog output cables are not electrically isolated
the recording device or the sensors must be zero-potential.
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