Physitemp Instruments TH5 - Manual (Page 7)

7.0 USE OF THERMALERT WITH A CHART RECORDER
7.1 Analog output is optional on Model TH-5.
WARNING: Use of AC-powered equipment with Physitemp Thermometers. As it is powered
entirely by low-voltage batteries, Physitemp Thermometer TH-5 presents no safety hazard to
patients. However, caution is advised when using the TH-5 with a chart recorder for recording
patient temperature. Such auxiliary equipment, when AC-powered and in faulty condition, can
create a potential shock hazard.
Hazard to a Grounded Patient
The circuit of the TH-5 is such that a low-impedance path exists from the analog output socket
to the probe input socket. The TH-5 with sensor probe could therefore act as an electrical con-
ductor between a faulty AC-powered recorder and the patient. Leakage current could exceed
safe limits.
Hazard to an Ungrounded Patient
Some chart recorders have a permanently grounded input binding post. If a patient is connected
to faulty AC-powered equipment and becomes live, a leakage path to ground would exist
between the sensor probe and the recorder. Current safety limits could be exceeded.
If recording is essential: Use a recorder which meets AAMI safe current limit standards.
Before connecting thermometer to recorder, consult a competent
engineer about shock hazard. Remove connector plug from ther-
mometer analog output when not in use.
7.2 A DC output with amplitude approximately proportional to instrument reading is provid-
ed from a stereo-type jack on the back panel. A mating plug is supplied for connection to the
recorder. This plug may be left in the socket until it is required for use. The output of the TH-5
is 2 kilohms impedance, so connection to a potentiometric recorder will not affect either the
calibration or accuracy.
Connection diagram for the plug:
7.3 Recorder sensitivity and pen zero must be adjusted so that the lines on the chart corre-
spond to the desired range of temperatures
7
NEGATIVE (RETURN)
POSITIVE (SIGNAL, OUTPUT)