Astar PhysioGo.Lite Electro - Current and Voltage Stabilization - CC and CV Mode; Figure 5.5. Rough Diagram of the Output Circuit of the Unit Working in CV Mode (One Channel)

5. Unit description
User Manual – PhysioGo.Lite Electro page 20 / 96
Current and voltage stabilization – CC and CV mode
In the range of electrotherapy, the unit may be operated in one of two modes:
• CC mode (constant current) – when output current is stabilized,
• CV mode (constant voltage) – when output voltage is stabilized.
In CC mode the current in patient’s circuit is independent (within certain limits) from the resultant of resistance
of skin, tissues, electrodes (with moist pads) and cables. Effective operation of the unit for very high resistance
is possible due to its structure. At the maximum current value of 140 mA, stabilization within a full range
of current intensity regulation is provided for resistance values from 500 to 750 Ω. For higher values of resistance,
the maximum obtainable current intensity is lower. It means that increasing on the keyboard current intensity
over the limiting value does not result in further increase of current in the output circuit. This will be signaled by
the blinking electrodes symbol and at the end of the treatment the information about poor contact of electrodes
will be shown on the display (see section 5.6.2). In the case, when resistance is too high (e.g. used electrodes,
electrode viscose pads are not moistened enough), the information about high resistance in the patient circuit
will be shown on the display (see 5.6.1).
In CV mode, the voltage generated by the unit, which value is set up on the keyboard, is spread out (according
to Kirchhoff voltage law) between the unit’s output resistance and resistance of a load. Rough diagram
of operation system in CV mode for one channel is presented in Figure 5.5.
Figure 5.5. Rough diagram of the output circuit of the unit working in CV mode (one channel)
Symbols used in figure:
− E – the value of output voltage – set on the keyboard
− Uout – drop of the voltage on unit’s output resistance
− Rout – unit’s output resistance
− U
L
– load voltage
− R
L
– load resistance
The value of voltage in the patient’s circuit depends on the quotient of unit’s output resistance by the resultant
of resistance of skin, tissues, electrodes (with moist pads) and cables. During the unit operation, on the display
there are shown the internal settings and voltage value in patient’s circuit.
It is recommended to use CV mode while performing non-stationary treatment procedures, e.g. combination
therapy of current and ultrasounds or using the point electrodes. A momentary loss of contact between
the electrode and patient’s body does not result in interruption of treatment procedure, contrary to CC mode.
The calibration settings for CC mode are being defined with the load which has a resistance of 500 Ω.
The calibration settings for CV mode are being entered in the idle operation mode of the unit.