CBL CO-Set Injectate Temp Probe LOA-7'9" 23001A Healthcare 989803101031

23001A Philipilip Healthcare 989803101031, CBL CO-Set Injectate Temp Probe LOA-7'9"

23001A Philipilip Healthcare 989803101031, CBL CO-Set Injectate Temp Probe LOA-7'9"

Temperature probes are an indispensable component of many medical equipment. After all, body temperature is one of the most direct responses to human health. It can be intuitively seen whether the patient is in an infection or low temperature state through temperature.

Classification of medical temperature probes

There are several types of medical temperature probes according to their applications, including disposable medical temperature probes, ablation temperature probes, and forehead thermometers and ear thermometers. Among them, temperature probes for disposable medical applications mainly use NTC thermistors; ablation applications use thermocouples; forehead thermometers and ear thermometers use thermopile technology.

NTC thermistor is a kind of heat sensitive semiconductor resistor, its resistance value decreases with the increase of temperature, the temperature coefficient of resistance is about 10 times that of metal resistance, the resistance value of NTC thermistor can be changed by the external environment The temperature change can also be caused by the current flowing through and self-heating.

The working principle of a thermocouple is formed by connecting two different metals to form a sensing junction. When the temperature of the sensing junction and the free end are different, the thermocouple will generate a voltage between the two wires. The voltage signal can be converted into a temperature reading. Medical "miniature" thermocouples refer to thermocouples made of wires with a smaller diameter, usually 38AWG (outer diameter 0.10mm) or less.

Forehead thermometers and ear thermometers, infrared thermometers using thermopile probes measure the radiant energy emitted by objects. According to Boltzmann’s law, the greater the radiant energy and the higher the object’s temperature, the infrared radiation signal It is converted into an electrical signal, and then through an amplifier and a signal processing circuit, and corrected according to a certain algorithm and target emissivity, it can finally be converted into the temperature value of the measured target. The main component of temperature measurement is the thermopile. The thermopile infrared probe is a temperature sensor composed of a series of thermocouples in series, thereby improving the detection sensitivity of the sensor.

Comparison of characteristics of temperature probes

We need to understand the difference in characteristics between different probes, the specific application areas are determined according to different characteristics

Linearity

Linearity defines the degree to which the sensor output continues to change over the temperature range. NTC thermistors are exponentially non-linear and exhibit higher sensitivity at low temperatures than at high temperatures. As time goes by, as the application of microprocessors in sensor signal conditioning circuits becomes more and more widespread, the linearity of the sensor becomes less important. When energized, both the thermistor and platinum resistance temperature detector need to carefully consider the power dissipated in the sensor element to prevent self-heating. For platinum resistance temperature detector probes, the measuring current is specified in the applicable standards (ASTM, DIN). There is no such standard for NTC thermistors. The design team only needs to determine the appropriate current level to confirm that there will be no obvious self-heating when providing sufficient signal-to-noise ratio. These currents are usually in the microampere range.

Response time

The response time or the speed at which the sensor indicates the temperature depends on the size and quality of the sensor element (assuming no prediction method is used). Among them, the IC temperature sensor has the slowest response, and the platinum thermal coil element is the second slowest. The platinum film, thermistor and thermocouple have small packages, so the response time will be fast, and the glass bead is the fastest responding thermal sensor. resistance. The response time itself is an undefined feature. Better thermal response measurement methods usually use the time constant (TC), which is the time required for the sensor to record a 63.2% temperature change when the sensor is transmitting between two different temperatures. As the name implies, this is a constant value for a given medium, independent of the starting temperature and ending temperature, and it is based on the basic Philipilipysical principles of heat transfer. For different media to be tested, there are different time constants. For example, the time constant measured in still air is 10 times longer than that measured in oil.

Electrical noise

Due to the weak millivolt signal of the thermocouple, the error caused by the electrical noise in the temperature indication is a major problem, but the NTC thermistor has a very high resistance, and the error of the electrical noise will be much smaller.

Lead resistance

Lead wire resistance may cause the error offset of resistive devices (such as thermistors or resistance temperature detectors). This effect is more pronounced in low-resistance devices (such as 100Ω platinum components or low-resistance thermistors). The relatively low temperature coefficient of the platinum resistance temperature detector makes the problem more complicated, so use a 3-wire or 4-wire lead configuration to subtract the lead resistance from the measurement. For thermistors, usually choosing a higher resistance value will eliminate this effect. Thermocouples must use extension leads and connectors of the same material as the lead itself, otherwise errors may occur.