
The Cal signal from the Control Board is used
both for input impedance testing and for the Amp
Cal signal.
In Impedance Check mode the full amplitude
signal passed through a 1M
Ω
resistor is switched
to each input in turn by a de-multiplexer. The
signal from the amplifier is interpreted by the
application software to determine the impedance at
the input and compares it to the impedance level
set by the operator. The mainframe then outputs
data to the headbox which turns on the LED’s in
the headbox to indicate the impedance level for
each channel.
In Amp Cal mode, the signal is attenuated by a
chain of resistors and the reduced amplitude signal
is routed to the input of the amplifier modules via
the cross-point switches.
A temperature probe can be connected to the
headbox via the Electrode Board. The probe signal
is input to an instrumentation amplifier and then
routed to the PIC on the Control Board. (There is
TECHNICAL OVERVIEW
Issue A May 1998
Synergy Mobile Workshop Manual
Chapter 4 Page 11
EP
INPUTS
EMG
1
IN
PUTS
EMG
2
IN
PUTS
EMG 2 CMR
REFERENCE
EMG 1 CMR
REFERENCE
EP CMR
REFERENCE
NEUT
RAL
INPUT
CROSS-POINT
SWITCHES
+/-5 ISOLATED
SUPPLIES
Z-CHECK
DECODE AND
DE-MULTIPLEXERS
AMPLIFIER
M
ODULES
Z-CHECK
LED'S
Z-CHECK LED
DE-MULTIPLEXER
STROBE
STROBE
STROBE
STROBE
STROBE
DATA
CLOCK
+/- REF.
SUPPLIES
SERIAL
DAC
CLOCK
DATA
D.C. OFFSET
CAL
AMP CAL SIGNAL
ATTENUATORS
CH1-10
TEMPERATURE PROBE
REMOTE PROBE
TEMP
SWEEP
GAIN
TRIGGER
AMP ON
INC_OHM
DEC_OHM
INSTRUMENTATION
AMPLIFIER
ROT
A
R
Y
SWI
T
CHES
AND
PUSH-BUTT
ONS
Figure 4-7 Schematic diagram of the 5 Channel Headbox Electrode Board