indoor temperature refrigerator thermometer

U-shaped manometer liquid, there are several specifications (you can also customize a larger scale):
Specifications Pa                    The largest measure of atmospheric pressure
± 500 0-1000                                                              0.13                 
± 1000 0-2000                                                       0.  26            
± 1500 0-3000                                                          0.39                 
± 2000 0-4000                                                       0.52                
± 2500 0-5000                                                         0.65                    
± 10000 0-20000                                                       2.62
± 3000 0-6000                                                           0.78              
± 4000 0- 8000                                                        1.50  
± 5000 0-10000                                                        1.31
 ± 6000 0-12000                                                        1.57
 ± 8000 0-16000                                                        2.10
 ± 10000 0-20000                                                      2.62
 ± 15000 0-30000                                                      3.93  
Use the U-type pressure gauge must be suspended vertically in a wall or stand on, then the pressure measured object the size of the U-shaped glass tube into the working fluid (mercury or colored water) into the volume as well as the ruler scale of 1 / 2 is appropriate.
1, the measurement must be taken before all the pressure gauge to measure the maximum pressure should be greater than or equal to the measured, to prevent the working fluid out of the tube mouth.

2, glass wall and work to maintain the purity of pure liquid, when not in use, the application of gauze or other coverings cover the nozzle, so as not to affect the determination of the exact position