M.I. P/N 004-2163 Rev. C
29
Care of Ultra-Miniature P-V Catheters
Proper Handling is Critical to Maximizing the Use-Life of Millar's Ultra-miniature P-
V Catheters. Refer to the Troubleshooting, System Maintenance, and Specifications
section of this document for important information.
Additional guidelines
Temperature Measurement
The system was designed assuming that the input to the temperature measurement circuit
will be a thermistor with a standard J curve and a resistance of 10kohms at 25degreesC.
This is the type of temperature sensor that is used in the rho cuvette. It is possible to use
the temperature measurement circuit in the MPVS
Ultra
to measure temperature from
another source. For example, a thermodilution catheter with an appropriate thermistor can
be connected to the system. The output of the temperature measurement circuit is available
on the rear panel of the MPVS
Ultra
. The user is responsible for calibrating the
relationship between voltage and temperature.
When making a custom cable to connect a temperature measurement device to the Cuvette
input, use the diagram below.
Pins 5 and 6 are the inputs to the thermistor. Do not connect to pins 1, 2, 3, or 4 since
doing so may damage the resistivity measurement circuit. Pin 7 may be used to ground the
shield of the cable. It is very important to note that all four front-panel inputs are isolated
from the voltage outputs, power input, USB input and equipotential point. However, these
four inputs are not isolated from each other. When using accessories not designed or
provided by Millar, the user assumes all responsibility for damage, harm, or loss resulting
from the use of these accessories.
Conductance, Conductivity, Resistance, Resistivity
It is important to note the differences and relationships among conductance, conductivity,
resistance and resistivity.
Resistivity and conductivity are properties of materials and are subject to the condition of
the material when it is measured. Just as with metals, the conductivity and resistivity of
blood is temperature dependent. The resistivity value used in volume calculation should
ideally be measured in blood that is representative of the study groups. At a minimum, be
sure to take species into account as resistivity varies between species. There is a noticeable
difference in the resistivity of blood and that of muscle. Size and shape do not affect
resistivity and conductivity.
Theor
y
of Operation
1
2
3
4
5
6
7
