testo 6651
- 1.2 Product description
13
1.2.3 Display and keypad
The display option allows the testo 6651 humidity transmitter to be operated
via the display and four keys.
The LCD display consists of two 7-segment lines for displaying readings and
units and of an information line (for status messages, for example).
The brightness and contrast of the display and the background lighting
(permanent or off) can be changed via the user menu or the P2A software.
1.2.4 Service interface
Behind the service flap is the parameterizing socket (mini-DIN) as an
interface to the P2A software or Testo handheld instrument
(testo 400/testo 650).
1.2.5 Relay board (option)
This has a floating switch capacity of 250 V AC/3 A. The switching limits and
hysteresis as well as the function as relay for the collective alarm can be set
via the display or the P2A software. Further features include:
Function of changeover contacts (NC/NO contacts) freely selectable
12 terminals for a total of 4 relays.
If no relays are available, settings for monitoring limit values
or alarms can still be controlled via the display.
Only have the transmitter wired and connected by authorized
personnel with the voltage disconnected.
1.2.6 Analog outputs
For analog outputs, the testo 6651 has either
2 current outputs of 4 to 20 mA (2-wire) / 0 to 20 mA (4-wire) / 4 to
20 mA (4-wire) or
2 voltage outputs of 0 to 1 V/0 to 5 V/0 to 10 V (4-wire).
In 2-wire operation, channel 1 is used for the supply. The two channels are
galvanically isolated in both 2- and 4-wire operation.
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