Calibration, Board layout, Procedure – Sensory Science 7405 User Manual
Page 5: Pin –pin gnd load
Sensoray Model 7405 Instruction Manual — Page 5
Channel connections should be made as illustrated in the
following diagram, regardless of the selected channel output
mode.
Calibration
Although the 7405 analog section is factory calibrated at
Sensoray, you may find that a periodic calibration is in order
to compensate for circuit drift over time. The board contains
nine trimpots in all, one offset trim for each channel and one
gain trim that is common to all channels.
The general strategy for board calibration is to first adjust the
gain trimpot, followed by the individual channel offset
adjustments. It is important that the final offset adjustments
be performed after configuring the channels for their target
operating modes.
Procedure
1.
Configure analog channel 0 for voltage output mode by
removing programming shunts at A0, B0 and D0.
2.
Connect a precision voltmeter to the channel 0 voltage
outputs. Connect the positive lead to P1 pin 2, and the
negative lead to P1 pin 4.
3.
Set analog channel 0 output to 0 volts by programming
the channel data value to 800 hex.
4.
Adjust the channel 0 offset trimpot until the voltmeter
reads 0 volts.
5.
Set analog channel 0 output to -10 volts by
programming the channel data value to 000 hex.
6.
Adjust the gain trimpot until the voltmeter reads -10
volts.
7.
Configure the output modes of all eight channels as
required by your application.
8.
For each voltage channel, connect the meter to the
channel voltage output pins on connector P1. Set the
output to 0 volts by programming the channel data value
to 800 hex. Adjust the channel offset trimpot until the
meter displays 0 volts.
9.
For each current channel, connect a precision
milliammeter across the channel’s current output pins
on connector P1. Set the output to 4 mA by
programming the channel data value to 000 hex. Adjust
the channel offset trimpot until the meter displays 4 mA.
Board Layout
Chan
Voltage
Mode Pin
Current
Mode Pin
+
-
+
-
0
2
4
1
3
1
6
8
5
7
2
10
12
9
11
3
14
16
13
15
4
18
20
17
19
5
22
24
21
23
6
26
28
25
27
7
30
32
29
31
+pin
–pin
gnd
load
CH0
B0
A0
CH1
B1
A1
CH2
B2
A2
CH3
B3
A3
CH4
B4
A4
CH5
B5
A5
CH6
B6
A6
CH7
B7
A7
GAIN
P1
E8
7
6
5
4
3
2
1
D7
0
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