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Coefficients Certificate Value
R(.01) R(273.16K)
aa5
bb5
c0.0
d0.0
a4 a5
b4 b5
7.9.10 IEC751
The IEC751 probe type is for standard PRTs (RTDs) conforming to the IEC751
or DIN-43760 standards. This type of probe is generally low cost and has a
wide operating range (–180°C to 420°C or higher), but has limited accuracy
(0.15°C to 4°C). There are no user programmable coefficients associated with
this probe type. Temperature is converted from resistance based upon the stan-
dard PRT table resident in the instrument.
7.9.11 CVD
The CVD (Callendar-Van Dusen) type is used with PRTs that have unique cali-
bration coefficients or do not match the IEC-751 specification. This type of
probe is generally low cost, has a wide operating range (–180°C to 420°C or
higher), and has moderate accuracy (0.05°C to 1°C). This type uses the
Callendar-Van Dusen equation to calculate temperature from resistance:
rt C
Rt
t
t
R
([ ])°=
+− −
⎛
⎝
⎜
⎞
⎠
⎟
⎡
⎣
⎢
⎤
⎦
⎥
⎧
⎨
⎩
⎫
⎬
⎭
≥
0
0
1
1
100 100
10αδ
1
100 100
1
100
1
100
3
+− −
⎛
⎝
⎜
⎞
⎠
⎟
−−
⎛
⎝
⎜
⎞
⎠
⎟
⎛
⎝
⎜
⎞
⎠
⎟
⎡
⎣
⎢
αδ βt
tt t t
⎢
⎤
⎦
⎥
⎥
⎧
⎨
⎪
⎩
⎪
⎫
⎬
⎪
⎭
⎪
<
⎧
⎨
⎪
⎪
⎩
⎪
⎪
t 0
The coefficients R0, α, δ,andβ can be set by the user using the functions
“R0", ”Alpha", “Delta”, and “Beta” respectively. When editing “Alpha” there is
an assumed 10
–3
exponent (i.e. 3.8500 is actually 0.0038500).
7.9.12 YSI-400
The YSI-400 type is for 2252Ω thermistors matching the characteristics of the
YSI-400 series of thermistors. This type of probe generally is low cost, has a
limited operating range (–40°C to 150°C), good accuracy (0.1°C to 0.4°C), and
excellent resolution (0.002°C). There are no user programmable coefficients as
-
sociated with this probe type. Temperature is converted from resistance based
upon a standard YSI-400 table resident in the instrument.
43
7 Display Functions
CAL MODE