External Analog Channel Input

Stephen Hanly

External Analog Channel Input

Objective

Enable an external analog input channel to use external sensors and/or synchronize recorded data to a known time stamp.

Description

Many of our recorders include a sensor that has an analog output that we are sampling at 20 kHz in each sub-channel. The processor and A/D converter we are using have 5 more channels that we aren't using, we'd like to extend a channel out of the enclosure for external sensors. We have done this customization for occasional customers but there are a few issues:

• No filtering or electrical protection
• Software treats the extra channel as "acceleration"
  Following the hardware update, a more formal extra analog channel option can be enabled that will include filtering and electrical protection. The software will also need to be developed to treat the extra channel as a separate channel to acceleration.

Requirements

• Include low-pass analog filters with user selectable frequency cutoffs
• Protection for voltages outside 0-3 volts and over current

Deliverables

• Hardware add-on to include two wires exiting the rear of the recorder for analog channel
• Software support to change units and scale this data

Cost to the Customer

The added complexity in manufacturing and assembly will add a $500 fee for units with this external channel.

Example Use Cases

1. IRIG Time Stamps: An engineering team is performing testing on a missile system and the time stamps are critical to correlate vibration/shock data to other sensors and systems. They have a voltage signal for the IRIG time stamps that they would like to use to synchronize recorded data.
2. External Pressure Sensor: A group is recording vibration data on an engine and they'd like to understand how the pressure inside the engine compartment changes over time and relates to vibration levels. They need a higher frequency sampling rate for this ability than the ambient pressure sensor included in the unit.