Testing Amplifier Impedance and Signal Response Times
This method of testing can be used to evaluate electrodes and amplifiers for damage. This is recommended if receiving inconsistent or inaccurate data during a session.
Testing Impedance Circuitry
Begin a live session with the amplifier connected to the computer.
Once the live session has begun, press Ctrl+F7 to open the impedance screen. Here we should see impedance readings for the Signal and Reference ports of active channels.
Without electrodes connected, this should report the following values depending on the amplifier used:A202/A404: 50k; one value for each Signal and Reference
U-Wiz/Q-Wiz: -2/256k, 256k, 0k; one value for each Channel
Optima 2/Optima+ 4: 125k; one value for each Signal and Reference
J202/J404: 2000k; one value for each Signal and ReferenceThis value indicates an ‘open’ connection, meaning the electrodes are not being touched together or on a client’s scalp. If this value is not reported, it indicates damage to the amplifier.
Insert electrodes into the Signal A, Reference A, and Ground ports.
Once the electrodes are inserted into the amplifier, touch and hold the metal contacts/sensors of all three electrodes together. This is simulating 'perfect' impedance, as there is nothing between the electrodes.
When doing this, we should observe the values decreasing to 1k, or close to that value. If all reported values stay at their open connection, or close to that value, try swapping out the electrode in the Ground port for another electrode. If the values then decrease, this indicates that the original ground electrode is damaged.
If one of the values stays at the open connection value, but another drops down, that may indicate that the electrode in the Signal or Reference port is damaged. Identify which electrode is reporting the open connection and replace it, and see if the new electrode reports a lower value.
If the amplifier reports an open connection with no electrodes connected, and drops down to 1k when electrodes are touched together, this tells us that both the electrodes and the amplifier's impedance circuitry are functioning correctly.
Testing the Signal Response
Press Ctrl+F7 to return to the Therapist/Wave Screen.
If the electrodes are still connected to the amplifier, we may observe some ambient noise on the RAW traces. Touch the electrodes again and see if this ambient noise flatlines. If it does not, try to move away any nearby electrical devices (smartphones, smartwatches, etc.) and see if the signal improves.
If the noise does not flatline, or is severe, that may indicate damage to the amplifier. Additionally, if the 'center' of the raw trace is above or below the middle line, or the signal appears to be 'wandering' up and down, that indicates damage to the amplifier.
Observe the Spectral FFT Bars at the bottom of the Therapist/Wave Screen - identify if there is a large and consistent spike in the signal and at what frequency it is. This can sometimes indicate damage to the amplifier or outside interference.
