Load Cell Wiring & Troubleshooting Flashcards

What is the typical color code for the excitation positive (+EXC) wire in a standard 4-wire load cell cable?

Answer: Red

In most standard load cell color conventions, red is used for the excitation positive (+EXC) lead.

A technician measures 0 mV output from a load cell under full rated load. Which fault is most likely?

Answer: Open excitation circuit

An open excitation circuit removes the bridge supply voltage, resulting in zero output regardless of applied load.

When wiring multiple load cells in a parallel junction box, what must be matched between cells to ensure accurate summing?

Answer: Input impedance of each load cell

Matching input impedance ensures equal current distribution across parallel-connected load cells for accurate summing.

What does a negative mV/V output reading indicate when a load cell is under a compressive load that should produce a positive reading?

Answer: Signal wires are reversed

A negative output when positive is expected means the signal+ and signal− leads have been swapped.

Which instrument is most appropriate for measuring the zero balance output (offset) of a load cell in mV?

Answer: Precision digital multimeter

A precision digital multimeter with mV resolution is the correct tool for measuring the small DC offset voltage of a load cell at zero balance.

What wiring configuration is used in a 6-wire load cell to compensate for cable resistance errors?

Answer: Separate sense lines feed back excitation voltage to the indicator

6-wire load cells add sense lines that allow the indicator to monitor and regulate the exact voltage at the load cell terminals, eliminating cable resistance drop errors.

A junction box trim potentiometer is adjusted to correct for what specific condition in a multi-load-cell system?

Answer: Corner or span errors between individual load cells

Trim potentiometers in a summing junction box allow individual cell output levels to be equalized, correcting corner and span errors.