Digital Load Cell

“A digital load cell is a combination of a conventional electrical load cell (strain gauge type) and a signal conditioning element to convert analog electrical output into digital form using analog to digital converter. Mostly, a digital signal is sent to the digital cell indicator to readout weight values and/ or controller to control crucial equipment process.”

A block diagram is shown below to define complete digital cell operation-

Block diagram of digital cell

Digital load cell working principle-

Since these load cells are conjunction of traditional analog load cell with an integrated microprocessor for signal processing, so their working is also based on load cell type used such as strain gauge type, piezoelectric type or capacitive type. Signal processing unit includes amplifiers, attenuators, filters, bridge circuits etc. and analog to digital converter to convert into binary output that is fed to microprocessor.

Digital Load cell circuit diagram

Microprocessor allows for improved system accuracy and load cell handling and diagnostics. The digital output is convenient for the users to readout via digital display or indicator and easy to communicate with each load cell independently within a system. They also offer greater flexibility to record date for log duration, control the crucial process and to send readings or communicate longer distance etc.

How Digital type cell is different from analog load cell-

Essentially, the difference between an analog and a digital type cell is how the weight signal is processed. Digital cell systems differ from analog systems in three important ways- signal strength, signal content, and data sampling rate. However the digital load cell price is higher than an analog one. Each are being described below-

  1. Signal Strength –

In a digital type cell, signals from a strain gauge (an instrument used to measure strain on an object) begin as an analog electrical voltage. A microprocessor inside the load cell instantly converts them into digital signals. Those digital signals typically use 2 to 6 volts as their signal range, which is less sensitive to fluctuations than the 0.03 volt range in an analog cell. In other words, the digital signal is too strong.

  1. Signal Content –

Analog systems rely on the electrical voltage from the load cell to determine the weight reading. In contrast, digital systems transmit data from each load cell. Signals are made up of binary information (values   of zero and one) as computers use them. Since binary data is not susceptible to interference from radio frequencies, electromagnetics, temperature, and other hazards, the binary data stream is more stable and less likely to be weighed down.

  1. Data Sampling Rate –

The data sampling rate measures how quickly a load cell can send weight information. Analog load cells provide continuous weight information in real time. Digital cells send weight information in bits several times per second.

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