Specifications

PK2100 Series Z-World 530-757-3737 4
Using the PK2100
Universal Inputs
Figure 3 below shows the six universal inputs and the high-gain
input. A seventh universal input is available if you do not use
the high-gain channel. (Note that the high-gain input is channel
6 and that the “spare” universal input is channel 7.)
Each input channel has a comparator that yields a 1 when the
input level is greater than a threshold, and 0 otherwise.
By placing a jumper at J9, you can (1) choose the fixed hard-
ware threshold (1.6V by default) or (2) use the internal DAC to
generate a threshold. When software generates the thresholds
using the DAC, you can compare inputs against as many thresh-
olds as you like. Z-World software compares against 1 or 2
thresholds for digital input; it compares against several thresh-
olds for analog input (using successive approximation).
Channel 5 (labelled U6) can be 4-20 mA current loop if you
connect pins 7 and 8 of H5.
The internal DAC channel usually generates the reference volt-
age for the inputs. However, if you connect the fixed hardware
reference at jumper J9, this DAC channel is available at UEXP
on the screw terminals.
High-Gain Analog Input
This input is useful for devices requiring higher input sensitiv-
ity, for example, thermistors or RTDs in a bridge. The input
range is 0–1.0V with 10-bit resolution. The gain at the plus and
minus inputs is 10 when jumper H7 is installed. If H7 is re-
moved, then the gain of the plus input becomes higher: 11. The
calibration gain and offsets are stored in the EEPROM.
The gain, when H7 is connected is
y = a
1
× (x
1
+ a
0
) – b
1
× x
2
[1]
where
a
1
is the positive side scale.
a
0
is the positive side offset.
b
1
is the negative side scale.
x
1
is the positive side input.
x
2
is the negative side input.
Note that b
1
= a
1
– 1 (with H7 not connected). If the negative
input x
2
is tied to ground, then the equation becomes
y = a
1
× (x
1
+ a
0
) [2]
or, solving for x1,
x
1
= y /a
1
– a
0
[3]
This equation returns the input voltage, given the reading.
Solving equation 1 for (x
1
–x
2
) in terms of y and x
1
yields
(x
1
–x
2
) = y/b
1
– (a
1
/b
1
– 1) × x
1
– a
0
× a
1
/b
1
[4]
If you want to change the gain of the high-gain input, change
R5, R11, and possibly RP5. These are factory set to 47K, 47K,
and 470K for a factory gain of 10 (or 11, if H7 is removed).
When differential inputs are desired, it is preferable to operate
with H7 removed, since the scaling difference between the
+10 volt reference
430Ω resistor, 4–20 mA loop,
channel 5 (U6) only. Connect H5:7–8
0.01µ
+
–
4.7K
comparator
LM339A
RP4
UINx
10K
3.3K
reading to U8 or U9
+
–
10K
reading to U9
Channels 0–5,
labelled U1–U6
Channel 6, high-
gain, not labelled
comparator
LM339A
RP6 b
10K
+
–
100 pF
RP5 a
470K
SOUT
RP5 b
AIN+
AIN–
R11
47K
470K
R5
47K
10K
+
–
10K
reading to U30
0.01µ
R23
comparator
LM339A
22K
+
–
DAC
U22
DACI0
DAV/R
RR
V/EXP
UEXP
10K
5.1K
J9
1.6V
22K
Channel 7,
labelled AD+
IO address is UINP bit 6
I/O address is DREG2, bit 7
I/O address is UINP bits 0–5
RP6 a
RN6
R28
op-amp
LM324A
op-amp
LM324A
H1
H7
Jumper H4 to H6 to pull up
Jumper H5 to H6 to pull down
+10 volt ref
. . . . .
Figure 3. Universal Inputs and High-Gain Channel