Service Manual

Revision A Model 340 Telemetry System 5-7
2006920-001
Calibration: Receiver Calibration
ECG Channel
1. Confirm the –3 dB points of the band-pass frequency are at least
2200 Hz and 3000 Hz between the input TP45 and the output TP17.
Confirm the filter gain of 2 at center frequency.
2. With input frequency set at 2700 Hz and 250 mVp-p at TP45,
adjust R106 until the dc voltage at TP10 is equal to the dc voltage at
TP46 ± 10 mVdc.
3. Sweep the input frequency between 2450 Hz and 2950 Hz at a rate of
approximately 25 Hz. Observe the 25 Hz waveform at TP19 with an
8 ± 1.6 Vp–p amplitude.
4. Confirm the PLL lock-in range. This is the frequency where it
first achieves lock, not the range over which it maintains lock.
PLL lock occurs at ≥2300Hz and ≤3100Hz. Confirm lock occurs at
2205–2450 Hz and2950–3245 Hz. Lock-in is verified by a logic low at
TP18.
5. Confirm the frequency response –3 dB points at TP19 are 5 and 50
Hz.
dB
UNITS
AC
VOLTS
888 888 888
Hz Generator
888 888 888
Hz Counter