Data Flow Systems TCU800, Installation And Operation Manual, Page: 48 / 162

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C h a p t e r 4
TCU Powered Submersible Transducer
Input commons on the TCU must be either AC neutral (with no voltage potential when referenced to earth
ground) or the negative terminal of a DC power supply.
Analog Level Transducer
The terminals for the analog interface are:
• ISO+24V (P2-16) – ISO+24V is a 24 VDC bias source voltage with a maximum source current of 100 mA.
• TGND (P2-20) – TGND is provided to terminate the shield of a shielded transducer cable. This terminal is connected
to the TGND terminal (P1-7) and the case of the TCU.
• (P2-22) – is the positive input for current and voltage signals.
• (P2-21) – is the positive input for current signals for an optional backup analog transducer.
• ANALOG- (P2-23) – ANALOG- is the return terminal for current and voltage signals. Additionally, ANALOG- is the
common return for both ANALOG 1+ and .
• SHUNT (P2-24) – SHUNT must be tied to ANALOG- for current signals for ANALOG1.
Jumping SHUNT to ANALOG- places a 250 Ω load across the and ANALOG- terminals, which converts the
voltage input to a current input.
1. Wire the power for the analog transducer according to the transducer manufacturer’s instructions.
2. Connect the positive current or voltage signal from the transducer to the terminal (P2-22).
3. If required by the transducer, connect from the ANALOG- terminal (P2-23) back to the return on the transducer.
4. For current signals, jumper the ANALOG- terminal (P2-23) to the SHUNT terminal (P2-24).
Wiring Notes:
• Because and are tied to a common isolated ground (ANALOG-), the TCU must be the
last device in a multiple device analog loop (see Figure “Externally Powered Nonsubmersible Transducer” for an
example).
• When using the isolated bias to power monitor points and the analog loop, the device can’t exceed 100 mA at 24 VDC.
Exceeding 100 mA will cause the analog signal to not operate correctly.
• Each digital input biased by the same 24 V can use up to 4 mA each.