DTS customers are using DTS data acquisition systems (DAS) in a variety of applications. During testing events, it is sometimes necessary to record power/voltage levels for the system(s) under test. In certain cases, such as with electric and hybrid vehicle testing, the power/voltage levels requiring monitoring exceed the tolerance levels of the DAS being used. This range capability can be achieved by utilizing a DTS Voltage Range Expander cable.
Background: DTS DAS Tolerance
By design, DTS DAS are low-signal voltage tolerant (+/-2.5V differential, 5V single-ended). Exceeding this voltage range can result in damage to the DAS.
Excessive or harmful voltages include:
- >+/-5V (with respect to Chassis) on any sensor input connection (+/-Ex and +/-Sig)
- >15V on power input pins
- ANY voltage to the “contact only” Event input
For TDAS G5 or TDAS PRO, specifically:
- The +V input power lines to TDAS must NOT be connected to TDAS chassis
Voltage Range Expander Cable
The Voltage Range Expander Cable allows for an increased input range from 5V to 800V and is immune to polarity reversal. Contact DTS Sales for pricing information.
Users can also create their own voltage expander utilizing a simple wheatstone bridge circuit with added input impedance on the source input lines.
NOTE: Refer to the User Manual/Hardware Specifications for your specific system and configuration for connector pinouts.
For ease of calculating the resistance value R, voltage range increases should be done in increments of 20V. Moving from a +/-5V range to a +/-20V range is a 4:1 increase. Therefore, the resistance (R) would be 1/4 the desired voltage range. Given the power rating necessary for such a large voltage drop across resistor R, current travelling through the resistor should be limited to less than a milliAmp. As such, the ratio calculation should be multiplied by 10,000.
With this calculation in mind, for every additional 20V increase over the standard +/-5V DAS input range, R should be increased by 50k-Ohms. Direct calculations using the above equation can be used for specific voltage input values, but this easy '50k-Ohms per 20V' rule is far simpler to remember and implement -- as standard resistor values tend to be available around 50k-Ohms increments.
Calculating the Sensitivity setting for use in SLICEWare is accomplished by using the equation shown in the figure above.
Using a Voltage Range Expander with SLICEWare
Configuring SLICEWare to use a voltage range expander is simple. Create a new sensor with the following settings:
EXAMPLE: Signal Generator w/Floating Ground, 15Vpp, 10kHz Square Wave
Data in this section was collected using a SLICE PRO SIM at 1 Mega sample per second with the above settings.
Average Peak Voltage (max / min): 7.6V / -7.3V