how to reduce loading effect

Electronic circuits employ signals to operate, communicate, and process information. When measuring the signal response of a device, it is necessary to connect a measuring instrument to the device. However, this connection changes the circuit behavior and introduces unwanted effects, known as loading effects. Reducing loading effects is crucial to ensure that the measurement accurately represents the circuit's performance. In this article, we will discuss some methods of reducing the loading effect.

Matching the Impedance

Impedance matching is the process of matching the impedance of the measuring instrument to the device under test. Impedance is the ratio of the voltage to the current of a circuit. When the impedance of the circuit and the measuring instrument matches, the loading effect is reduced, and the measurement is accurate. Impedance matching can be achieved by using a matching network, attenuator, or amplifier. The choice of impedance matching method depends on the frequency range and the impedance of the circuit.

Using High Input Impedance Instrument

The loading effect is reduced by using an instrument with a high input impedance. The input impedance is the resistance that an instrument presents to the circuit under test. A high input impedance instrument will draw less current from the circuit, causing minimal disturbance to the circuit’s behavior. Using a high input impedance instrument is ideal for measuring low power devices, voltage, and small signals.

Minimizing the Connection Time

The loading effect increases with the connection time. The longer the connection between the measuring instrument and the circuit, the greater the disturbance to the circuit's behavior. Therefore, minimizing the connection time is an effective way to reduce loading effects. It is advantageous to use a switchable, multiplexed, or scanning system to minimize the time for each measurement.

Shielding the Connections

Electromagnetic interference (EMI) can introduce unwanted effects on the circuit's behavior due to the connection between the measuring instrument and the circuit. Shielding the connection is recommended to reduce the effect of EMI. Shielding can be achieved by using shielded cables, twisted pairs, or coaxial cables. Shielding the measuring instrument and the circuit connection helps to minimize the EMI disturbance and noise, thereby increasing the accuracy of the measurement.

Conclusion

Loading effect is a significant problem when measuring electronic circuits, and it is necessary to reduce it to ensure the measurement is accurate. Impedance matching, using high input impedance instrument, minimizing the connection time, and shielding the connection are effective ways to reduce loading effect. Employing these methods can significantly improve circuit performance measurements and prevent errors.