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Technical overview
System description
The Spot Vital Signs automatically measures systolic and diastolic blood pressure, pulse
rate, pulse oximetry (SpO
2
), and temperature (oral, axillary under 4 years, and rectal) for
adult and pediatric patients (excluding neonates).
The device is intended to be used by clinicians and medically qualified personnel. It is
available for sale only upon the order of a physician or licensed health care provider.
Refer to the Spot Vital Signs Directions for Use manual for complete information.
Battery /charge system
Spot Vital Signs includes a 6 Volt, 4.5 amp-hour sealed lead-acid battery that supplies all
power to the device. A polarized connector protects against reversing the battery
connection. An external power supply charges the battery and can operate Spot Vital
Signs at the same time. The external power supply provides the Spot Vital Signs with up
to 1000mA at 7.2VDC. As the battery charges, the energy required to charge it decreases
and the external power supply voltage rises to 8 VDC while supplying 750mA. The voltage
to the external power supply is approximately 12.5VDC with no load attached. The Spot
Vital Signs monitors the battery voltage to control the fast and trickle charge modes. The
CPU allows fast charge until the battery reaches approximately 7.0 VDC, and then the CPU
switches the charger circuit to trickle charge mode. For a dead battery the external charger
supplies sufficient power to allow the Spot Vital Signs to power on, but not enough
energy for a blood pressure cycle. A 5 amp surface mount fuse is populated on the Spot
Vital Signs main board at location F301.
Main CPU power supply
A single +5VDC linear regualtor (U319) powers the CPU and provides power to other
digital circuitry on the main printed circuit board.
Clock/calendar power
The battery directly powers the internal real time clock (U309) through a voltage divider.
The Spot Vital Signs always has power if a battery is connected. A 100uF capacitor (C308)
delivers energy to the real time clock during a battery exchange. If the battery is
disconnected for longer than 1 minute, reset the real time clock after restoring the battery
power.
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