ic-wt iC-Haus, ic-wt Datasheet - Page 10

• Manufacturer Part Number: ic-wt
• Description: Incremental Encoder
• Manufacturer: iC-Haus

MEASUREMENTS WITH THE DEMO BOARD
The iC-WT can be examined at three different levels:
1. Static wiring of the sensor inputs with constant currents (using DIP switches)
2. Dynamic wiring of the sensor inputs using function generator and current mirror circuit
3. Dynamic wiring of the sensor inputs using a rotary encoder with photodiodes array
A regulated power supply of +5V dc must be applied between VCC and GND for all measurements. Since the
iC-WT operates with very low sensor currents, the work surface should possess an insulated screen (e.g. a
single sided copper-clad plate) which is connected to GND. AGND is pulled down to GND inside the iC-WT and
should not be interconnected externally. The transmit LED of the rotary encoder can be connected between
LED and VCC. For the visual check in case of measurements without rotary encoder a colored LED is
recommended.
1.1 Static function of A, B and Z
Shut off the AND operation of index signal Z with A and B by connecting the combined input/output NERR to
ground; the red control LED will light up. The two trimming potentiometers should be in the middle position
initially, the DIP switches opened.
Closing a DIP switch of No.4 to No.8 connects the corresponding sensor input to AGND via a resistor (R4 to
R8). Since each input is at constant (but temperature-dependent!) voltage potential V(T), a constant current
results of the magnitude:
The result at room temperature is about:
This current is supposed to simulate the photocurrent of an illuminated photodiode. An open switch simulates
a diode which is not illuminated (I= 0).
The tracks A and B are evaluated differentially. The corresponding output is high (low) when current is only
flowing from the P(ositive) (N(egative)) input. If the two inputs are conducting no current or the same current,
the output remains in its old state due to hysteresis.
Track Z is compared to a current threshold set using the trimmer RZ. If the input current is higher, the output
Z is high. The current flowing from IZ is specified with RZ:
The current threshold set is obtained with the aid of the current transmission factor CR(IZ) as:
When the trimmer is at the middle setting, the following applies:
The resistance value set with RZ can be measured after removing the jumper JZ.
1.2 LED current control and error output
The function of the current control can be checked with an LED connected between LED and VCC. The voltage
at NERR is displayed by the red LED on the demo board. It lights up when NERR is active, i.e. low.
The setpoint of the receive power is set at pin ILR by using trimmer RLR. The resistance value can be
measured after removing the jumper JLR. The receive power is defined as the sum of the currents at the input
pins DPA, DNA, DPB and DNB. The setpoint I
or:
iC-WT
INCREMENTAL ENCODER
I= V(T) / R.
I= 1.8V / 4.3M
I
I
I
I
RLR= V(ILR) / (I
IZ
th
th
SUM
= V(IZ) / (CR(IZ)
= 1.22V / (400
= V(IZ) / RZ
= V(ILR) / (RLR
SUM
= 420nA
12.5k ) = 244nA
RZ)
CR(LR))
CR(LR))
SUM
is:
Rev A0, Page 10/13