User`s manual

7800 Series Hysteresisgraph System User's Manual
2-2 Theory of Operation
Theory of Operation (Continued)
The Lake Shore 7800 Series Hysteresisgraph measures and characterizes the DC properties of a variety of
magnetically “hard” permanent magnet materials.
Materials that can be tested with the 7800 Series Hysteresisgraph include:
• Alnico.
• Hard ferrite.
• Neodymium-iron-boron.
• Samarium cobalt.
• Other hard magnetic materials in any bulk form including cast, sintered, and bonded compounds.
• Compacted magnetic powders.
• Soft magnetic materials including transformer steel and relay steel-these materials can be evaluated for
saturation induction and relative performance.
• Ferrofluids-hysteresis loops can be evaluated for saturation values and loop shape; physical sheer forces may
prevent accurate measurement of some loop shape-dependent properties or lead to rate-dependent effects.
The 7800 Series Hysteresisgraph measures and derives:
• Normal curve B versus H.
• Intrinsic curve (B-H) versus H and J versus H.
• Second-quadrant demagnetization curves.
• Four-quadrant major and minor hysteresis loops.
• Recoil loops.
• Initial magnetization curve.
• Remanence, B
r
.
• Normal coercivity, H
c
.
• Intrinsic coercivity, H
ci
.
• Energy product, BH
max
.
• Knee-shape parameters, H
k
, and others.
• Permeance (load lines) with slope, B, B-H, and H coordinate queries.
Computer
Keyboard
Mouse
Printer
Monitor
(15 in. Flat/
17 in. CRT)
Parallel Port
IEEE-488
COM1
COM2
Modem
(Remote
Diagnostics)
Serial Micro-
meter/Caliper
(Optional)
Electromagnet
Model 218
Temperature
Monitor
Model 480
Fluxmeter
(B, B-H)
Model 480
Fluxmeter
(H)
Model 450
Gaussmeter
Video
IEEE-488 Bus
Power Supply
H Coil
Analog
Programming
Voltage
DC Current
B/B-H Coil
Hall-Effect
Probe
Analog
Analog
Analog
Sample/Bottom
Pole Temp. Sensor
Ambient
Temp.
Sensor
7800 Block.eps
Figure 2-1. 7800 Series Block Diagram