Hitachi Microscope & Magnifier S-4800 Manual De Usuario

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1.1.6  Stray Magnetic Field 
 
You should measure the stray magnetic field at the place for installing the Model S-4700 in 
advance.    When the requirements given in Table 1-1 are satisfied, no image trouble will occur.   
Avoid locations at which abrupt electric current change or magnetic field change might occur due 
to the presence of a large-sized magnetic clutch or power cable for other equipment.   
 

Table 1-1    Stray Magnetic Field (at image recording) 

 

 

Acceleratin
g Voltage 

Working 
Distance 

Magnification

Frequency 
Component 
Synchronous 
with Power 
Supply AC 
Magnetic Field 
(effective value) 

Frequency 
Component 
Asynchronous 
with Power 
Supply DC 
Magnetic Field 
Fluctuation 

Change with 
Time (drift) 

Allowable 
value 

15 kV 

4 mm 

220,000

×

 

290 nT 
(horizontal) 
220 nT (vertical) 

320 nT 
(horizontal) 
240 nT (vertical) 

600 nT/min 
(horizontal) 
450 nT/min 
(vertical) 

 

1 kV 

1.5 mm 

120,000

×

 

150 nT 
(horizontal) 
130 nT (vertical) 

170 nT 
(horizontal) 
150 nT (vertical) 

310 nT/min 
(horizontal) 
280 nT/min 
(vertical) 

nT:  Nanotesla 

 

 

 

NOTICE:  1.  The frequency component synchronous with power supply (AC magnetic field) is 

an effective value.    Therefore, its allowable value should be increased to 2.8 
times for evaluation in terms of p-p (peak to peak) value. 

2.  The DC magnetic field fluctuation stands for a rapid change of stray magnetic 

field with time lapse.    A gradual and moderate change with time lapse is 
handled as a temporal variation (drift).   

3.  The temporal variation (drift) of stray magnetic field signifies a difference 

(maximum drift) between the maximum and minimum levels within the specified 
time (1 minute).   

4.  The allowable value of AC magnetic field is determined so that image distortion 

(elongation, contraction or curving) at the specified magnification will not exceed 
0.5 mm.   

5.  The allowable value of DC magnetic field fluctuation is determined so that image 

disturbance (image shift or spike noise) at the specified magnification will not 
exceed 0.2 mm on a micrograph.   

6.  The allowable value of temporal variation (drift) in stray magnetic field is 

determined so that image sway due to that temporal variation will not exceed   
0.5 mm on a micrograph taken at the specified magnification.   

7.  Fluctuation-free DC component (excluding terrestrial magnetic field) of stray 

magnetic field will not cause the electron beam to sway.    Therefore, image