Section 4
4-18
T
n
Fine
= Int[ 648 x (Rx/Rs)]
and
T=
Tt
t
+
nV t +I)- nV(t -I)
nV( t I)-nV( t I)
n
Fine
n
Rough
Int 648
648
2
648
1
1
(, ,
,,
Regular Measurement Phase
a) Ix = ±(I
TEST
)
b) Tracking dac is started
c) Tn = T
n
Fine
d) t = 1
e) the ratio (Rx/Rs) is shown as a nine digit number
For measurements where the resistance ratio is
≥ 10:1 the servo signal can be slewing 20
V at a 1 second time constant. Hence, the flux detector output will be unbalanced for a
relatively long time on all transitions, so that the first measurement reported is not very
trustworthy. However, second and subsequent measurement cycles will be valid since they
invoke the tracking dac and the flux detector will barely see any transitions.
Note that the formula given for
T
n
Rough
is a special case of the formula for T
n
Fine
if we let
T
n
Rough
=t=324.
Note also that nV(±T,I) refers to the nanovolt detector reading with current Ix = I ;
turns Nx = "Null turn"±T turns, and Int(x) is the integer part of the real number x, for
example Int(4.7)=4.
The values
I
TEST
and Reversal Rate are the values entered in the <Setup Menu> for the
measurement configuration.
The displayed ratio is always Rx/Rs.
To Next Page
Loading...