1.1st, breath medical service surveillance meter
Uses for to monitor the breath condition, and can produce the approximate breath depth. This monitor meter monitors some may use for to appraise the anxious degree the important parameter: Breath frequency, between breath level of uniformity as well as expiration and inspiration intermittence. Tranquil, the positive mood usually can cause to exhale long to the inspiration, the two ratio of time promulgates person's to be anxious degree from an aspect. Relatively compares the high level 胸呼�?(to be opposite to abdomen breath) also may explain the anxious degree. Regarding 胸呼�?the observation may increase monitors the meter the visible information.
1.2nd, intelligent sensor technology
Chart 1 the center surveillance meter uses the silicon to press the anti- sensor (PRT) to examine the inspiration with exhales when corresponding pressure reducing with the increase. The PRT output �?enters a MAX1450 signal to recuperate IC, uses in carries on the adjustment to the PRT inherent error, then the voltage signal which compensates the process sends in 12 modulus switches ADC. The ADC output (digitized pressure signal) then enters a PC connection, and by the transformation is the RS-232 level. Finally the signal is transmitted PC, like this may demonstrate the breath profile, and states the parameter to above to carry on the analysis.
2nd, PRT sensor
2.1st, PRT examination principle
The PRT general disposition is a close wheatstone bridge. When has the pressure will exert PRT the sensitive electric bridge (sees attempts 2a to show), the opposite angle 桥臂 resistance value will have the same direction, the same size change. When opposite angle 桥臂 on two resistance values increase when the pressure function, moreover an opposite angle 桥臂 resistance value reduces, vice versa. (Sees regarding half sensitive electric bridge PRT attempts 2b to show), then only has the half 桥臂 resistance value to have the reform. No matter is the entire bridge or half sensitive electric bridge PRT sensor all has the high sensitivity (>10mv/v), the good linearity and the temperature stability, stagnates and so on the merit without the signal, its survey scope may on to the destructive limit.
2.2nd, PRT application
Now, because the new IC technology already could precisely calibrate passes on the PRT feeling, therefore its application scope, the low accuracy examination expanded to the high end domain in. Solved formerly the PRT sensor usually only to be able to use in the center, the low accuracy examination must use deficiency and so on expensive strain gauge in the high end product
3rd, the signal recuperates IC and the modern age and with the simplification adjustment plan
Because the PRT sensor erroneous scope scope is very wide, thus must have to use through the present modern age and the simplification compensation method calibrates. At present newest uses for to calibrate the PRT sensor error the signal to recuperate IC to have two kinds, one is MAX1457, two is MAX1450.
3.1st, modern age and adjustment plan
MAX1457 it has to use in to actuate the sensor to control the current supply and sampling sensor bridge connection voltage ADC, this voltage is the electric current output current and with the temperature correlation bridge connection resistance product. MAX1457 contains EEPROM and so on Through is the MAX1457 design application software calculates four kind of correction factors: Full outputs (FSO), temperature (FSOTC), displacement (Offset), temperature displacement (OffsetTC) Revises the error
Because MAX1457 provides the precision may far be higher than a breath to monitor the meter the request, namely is not unnecessary to use 16 resolution DAC to carry on the adjustment, but MAX1457 its temperature error compensates the ability also is has the necessity very much regarding not the great temperature change: 10 �?is accommodating the regular meeting fully to create PRT to output (FSO) to have 3% change, really because MAX1457 causes to monitor the meter to be allowed to work in the very wide temperature range, may obtain the precision using PRT and the MAX1457 combination which surpasses therefore it to be able to apply to domain and so on space conquest and diving respirator.
3.2nd, simplification adjustment plan
MAX1450 signal recuperating (see Figure 3 shows) the function essence and MAX1457 is same, only is replaces DAC with the resistance to carry on the error correction. Because MAX1450 uses MAX1457 to be much less than 校准�? its precision is 1%. Usually uses in to mix the plan, this plan and (all gave the light trimming resistance MAX1450 outside to meet resistance) to unify has provided one kind of low cost solution, namely might provide 1% precision with the MAX1450 signal recuperating coordination exterior laser trimming resistance. Adjusts the RFSOA resistance is the hypothesis initial (FSO) the sensitivity, the temperature deviation adjustment is after feeds back the sensor to drive the dynamic electricity the voltage (to come from the BDRIVE pin) to realize, completes the deviation by the PGA program control amplifier compensating.
On this occasion does to the MAX1450 pin function as soon as introduced that,
INP sensor signal input;
SOTC temperature displacement signal input;
The A0 program control amplifier (PGA) increases the establishment most low position input;
The A1 program control amplifier increases the establishment;
The A2 program control amplifier (PGA) increases the establishment most top digit input;
OFFTC displacement temperature correction;
OFFSET shift control input;
BBUF belt cushion electric bridge voltage input;
The FSOTRIM electric bridge actuates the electric current establishment input;
OUT program control amplifier output voltage;
ISRC current supply datum;
BDRIVE sensor exciting current input;
INM sensor negative signal input;
VDD supply voltage;
VSS