NOTE: The following Daytronic “3000 Series” manuals are also to be furnished with the Model TM3:
Model
3170 Strain Gage Conditioner; Model 3200/3300 Digital Indicator; and Model 3300 Hi-Lo Limits.
1. General Description
The Model TM3 is a version of the Model 3370P Strain Gage Conditioner (Peak Capture) that has
been specially adapted for automatic detection, display, and evaluation of the analog peaks experi-
enced by a single
torque-signal channel. Specifications for bandwidth, accuracy, and resolution of the
TM3 are identical to those of the Model 3170 (see
3170 Manual).
Continuous ratiometric excitation is applied to the torque-sensing element via four- or seven-wire
cabling (see below). The resulting millivolt torque signal is then amplified and processed for normal-
mode noise reduction. The conditioned signal is directly monitored by a real-time
analog peak capture
circuit containing a threshold of 15% of full-scale analog output (full scale = ±5 V-DC). The threshold
is necessary to avoid false triggering of the TM3’s
auto-reset circuit when seating the tool socket on
the bolt to be tightened.
An analog capacitor stores the rapidly increasing torque signal produced by application of mechanical
torque to the bolt. As soon as the threshold detects a drop of 15% in the live torque signal, a “HAVE
PEAK” condition is registered. This triggers a delay timer, allowing accurate analog-to-digital engineer-
ing-unit conversion. Displayed on the TM3’s front-panel LED display, the captured peak value is digi-
tally locked to avoid long-term signal decay. A second one-shot timer triggers after the digital hold to
discharge (or “auto-reset”) the storage capacitor, re-enabling the TM3 for another peak capture. Also
on application of the digital hold the current peak reading is evaluated against preset HIGH LIMIT and
LOW LIMIT setpoints. Front-panel LED’s provide direct indication of limit status: HIGH VIOLATION,
OK, or LOW VIOLATION. Corresponding TTL-level logic signals are available for external control
action (see
3300 Manual for details).
2. Connections
Refer to the
Model 3170 Manual for 4-wire or 7-wire transducer cable connections (7-wire cabling is
recommended to eliminate distributed temperature effects on the wire). Certain torque sensors require
5-volt excitation to reduce excitation current and heating effects (120
Ω
or less).
The TM3’s I/O CONNECTOR is located on the rear of the unit. Note that
a.
PIN 10 MUST BE TIED TO PIN K IN ORDER FOR THE TM3’S ANALOG PEAK CIRCUITRY TO
WORK PROPERLY.
b.
NO “EXTERNAL RESET” IS AVAILABLE, SINCE THE RESET FUNCTION IS ACCOMPLISHED
BY THE INTERNAL “AUTO-RESET” CIRCUIT.
c.
PIN 8 is for synchronization of the TM3 when it is used as a remote unit to a Daytronic “System
10.” The signal from Pin 8 would be received by the System 10 via a Model 10AIO-16 or 10BIO-
16 Universal Logic I/O Card.
d.
Analog outputs are available for monitoring at the TM3’s PIN 10 (live torque) and PIN 7 (momen-
tary voltage of captured peak).
e.
All remaining pins relate to
TTL-logic I/O for remote connection of “GO — NO GO” conditions (see
3300 Manual for details).
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