Analog Inputs. Drew Technologies DashDAQ XL, DashDAQ Series II

Imagine that you changed tires from 185/60-14 to 195/55-14 and now the speedometer is incorrect because you haven’t reprogrammed the ECM. The internet says that there would be a -1.3% difference and you want to compensate for that on the speed gauge. This calculation looks like:

Constant Multiplier = 0.987

Adjusted Speed = Constant Multiplier * Vehicle Speed

To perform this calculation on the DashDAQ, try setting:

• Input Signal: Vehicle Speed from GenericOBD2

• Multiplier Signal: Constant Multiplier from Rescale Signal Calculator

• Multiplier Sign: 1 (Positive)

• Constant Multiplier: 0.987. This represents 100% minus 1.3%.

• Offset Signal: Constant Offset from Rescale Signal Calculator

• Constant Offset: 0 to add/subtract nothing

The calculated value will be available when you assign signals to a gauge (section 0).

STATISTICS CALCULATOR (MIN / MAX / AVERAGE)

DashDAQ can calculate and display several statistics about a signal. Make sure that the “Statistics Calculator” was selected when reflashing the firmware (section 0) and install the driver on an available port (section 0). This calculator can be installed several times; once for each signal that you wish to average.

This driver has a few parameters:

• Input Signal: Signal for this calculation.

• Time to Average (s): Seconds of historical data to use in the calculation. For example, specify “1.5” to consider the past oneand-one-half seconds of data.

• Name: Abbreviation to identify this signal. Displayed on the assign signals screen.

• Precision: Number of decimal digits to display.

After configuring, you may choose among several calculations on the assign signals screen:

• Minimum: Smallest value during “time to average”

• Maximum: Largest value during “time to average”

• Smoothed: Average value during “time to average”. Using this signal with a small (1-2 second) time to average is a great way to filter signals that fluctuate wildly.

If you’ve assigned a statistic to a gauge but you’re not seeing values, double-check the Input Signal setting. Try assigning the input signal to a gauge to verify that the DashDAQ is able to get a reading.

ANALOG INPUTS

DashDAQ has two analog inputs available on the accessory connector. They accept a 0-5v DC signal and are compatible with most automotive sensors. These signals can be displayed on the gauge screens along with any other input. They can be rescaled from the 0-5v scale into Fahrenheit, PSI, Air-Fuel ratios, or whatever the voltage represents. The analog inputs on DashDAQ have a 24.7 kiloohm input impedance and may not be accurate when connected to a device with a high output impedance. For example, a narrowband O2 sensor output cannot be connected directly to a DashDAQ because the output impedance of the sensor is in the megaohm range.

There are two drivers included with DashDAQ, the Linear Analog driver (Analog Input) and Non Linear Analog Driver (Non Linear Analog

Input).

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The Linear Driver is for measuring signals that have a constant input voltage change for a given change in what’s being measured. An example is a sensor that has a 0.1V output change for every temperature degree it’s measuring. 3 terminal sensors that have a voltage input, a voltage output, and ground are often linear sensors.

The Non Linear Driver is for measuring signals that do not have a constant input change for a given change in what’s being measured.

An example is a NTC (negative temperature coefficient) type resistive temperature sensor, which is very common in vehicles. The NTC temperature sensor will change resistance by a few ohms per degree at high temperatures and many thousands of ohms per degree at cold temperatures. 2 terminal resistive temperature sensors are usually non-linear.

The 10-pin DashDAQ accessory cable must be purchased to connect these sensors and is always available at DashDAQ.com.

CONNECTIONS AND WIRING

Connect the analog input signal you wish to measure to either Analog In 1 or Analog In 2 on the DashDAQ. See the end of this manual for the I/O cable wiring table.

LINEAR ANALOG INPUT DRIVER SETUP

To setup an analog sensor in DashDAQ (sensor pre-wired to accessory cable assumed, see section 0):

1. From the DashDAQ Main Menu tap on [Setup], then [Devices], then [Manager].

2. A DashDAQ typically comes in original packaging with analog sensors pre-populated in the Device Manager. If you do not see

“Analog Input” in any of the driver slots (a-h) then tap on an empty slot and tap [Add Device].

3. Use the [<] or [>] buttons at the top to find the “Other” heading. Tap on [Analog Input] to highlight and tap [Install].

4. Select which port (analog-1 or analog-2) you would like to use. (Figure 29)

5. Your analog sensor is now specified as a input in the Device Manager and can be assigned to any gauge to be viewed as voltage. To understand how to scale the signal to a specific unit see the next section (Section 0).

Figure 29: DashDAQ comes preloaded with both Analog Inputs. If you needed to reinstall, you’d use Device Manager to install AnalogInput in an available slot

Figure 30: Then you’d specify either Analog-1 or Analog-2. To read both, just load the driver twice in two different slots.

LINEAR ANALOG DRIVER CORRECTION FACTOR AND CORRECTION OFFSET

Let’s pretend that you have an Innovate LC-1 wideband controller and you’d prefer to see an Air-Fuel ratio instead of a raw voltage.

DashDAQ is able to convert a linear raw voltage signal into physical units using the following formula:

Corrected Value = Correction Factor * Raw Voltage + Correction Offset

This procedure will help you find values for Correction Factor and Correction Offset. The LC1-1’s instruction manual says that its 0-5v analog output represents AFR=7.35 to AFR=22.39. With that information you can setup two equations:

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Correction Factor * 0v DC + Correction Offset = 7.35

Correction Factor * 5v DC + Correction Offset = 22.39

The first equation is pretty easy because zero times anything is zero. We quickly realize that:

Correction Offset = 7.35

Using that number, and some basic algebra, you solve the second equation and determine:

Correction Factor * 5v DC + 7.35 = 22.39

Correction Factor * 5v DC = 15.04

Correction Factor = 3.008

With this procedure and two known-values, you can determine the Correction Factor and Correction Offset for most automotive sensors. If you need assistance please post on the user forums at DashDAQ.com. Be sure to include a link to the user’s manual of your sensor!

CONVERTING AN ANALOG VOLTAGE INTO PHYSICAL UNITS

Navigate to “Parameters” by tapping on [Setup] from the Main Menu, then [Devices], then [Parameters]. Use the arrows at the top to find the analog input you would like to scale.

Figure 31: Setting parameters for an analog input

These parameters are used when converting an analog signal into physical units:

• Correction Factor: Multiplier for the raw voltage. Described in section 0.

• Correction Offset: Added to the raw voltage Describe in section 0.

• Corrected Reading Name: Abbreviation to identify corrected signal. Used as a gauge label and displayed on the assign signals screen.

• Corrected Reading Units: Physical units for the calculation. Any automatic Imperial/Metric occurs afterward. For example, if a calculation results in °C the number could be automatically converted to °F before display.

• Corrected Reading Min: Default minimum value; used for round gauges and graphs. You can override this for each gauge on the assign signals screen

• Corrected Reading Max: Default maximum value; used for round gauges and graphs. You can override this for each gauge on the assign signals screen

NON LINEAR ANALOG INPUT DRIVER SETUP

To setup an analog sensor in DashDAQ (sensor pre-wired to accessory cable assumed, see section 0):

1. From the DashDAQ Main Menu tap on [Setup], then [Devices], then [Manager].

2. Tap on an empty slot and tap [Change]. 35

3. Use the [<] or [>] buttons at the top to find the “Other” heading. Tap on [Non Linear Analog Input] to highlight and tap [Save].

4. Now notice which port is specified on the change device screen. The black box next to the [Port] button contains a sensor number that should correspond to the number of the Analog Input that the sensor is connected to. If it does not tap the [Port] button once for the other analog input.

5. Tap [Save]. The analog sensor is now specified as an input in the Device Manager and can be assigned to any gauge to be viewed as voltage. To understand how to scale the signal to a specific unit see the next section (Section 0).

NON LINEAR ANALOG INPUT CONFIGURATION

The Non Linear Driver is configured by the use of a configuration file. The nature of the configuration file will be covered in the next section. To configure the driver:

1. From the DashDAQ Main Menu tap on [Setup], then [Devices], then [Parameters].

2. Tap on the [<] or [>] until the letter for the Non Linear Driver being configured is shown.

3. Tap on a parameter to highlight it and tap on [Change] to change that parameter. The parameter meanings are as follows:

• Conversion Data Filename: This is the name of the configuration file name. By default the file is named either

“analog1.config” or “analog2.config”, depending on which port this driver is configured for. The file name root can be anything, but the suffix must be .config in order to install it.

• Signal Name: This is the name that will show up on the gauge.

• Units Name: This is the physcial units type (degC, kPA, PSI, etc). This will be displayed on the gauge if the gauge has enough room to display it in full. This is also used to do automatic English <-> Metric conversion. The units name must be exactly match one of DashDAQ’s standard units values in order for English <-> Metric conversion to work properly. The current units conversion set is shown in Appendix B.

NON LINEAR ANALOG INPUT DRIVER CONFIGURATION FILE

The analog inputs of DashDAQ have 10 bit A/D converters. This means that there’s 1024 discrete readings possible on each A/D input.

The actual input measuring range for the A/D converter is 0 to 5.035V in 1023 steps, with the 1024 th

step being anything over 5.035V, so each step is (5.035/1023), or approximately 0.00492 volts.

The configuration file consists of 1024 ascii numbers separated by any non numeric character except ‘.’, ‘+’, or ‘-‘. Each number in the configuration file is what will be displayed for that voltage step on the input. For example, if you created a file that had the ascii numbers 1 to 1024 in it separated by spaces, for voltage inputs from 0-0.00492V the DashDAQ would display 1, for 0.00492-0.00984V the DashDAQ would display 2, continuing to 5.030V to 5.035V would display 1023, and finally 5.035V or greater would display 1024.

Given the DashDAQ input impedance of 24.7 Kohm and knowing the resistance or voltage output of a given sensor over the range that is to be measured, it’s possible to create a configuration file for most resistive and amplified sensor types. The sensor setup options and calculations involved in creating the file are beyond the scope of this manual and will be covered in a separate application note.

Once an appropriate configuration file has been generated, it must be installed on DashDAQ from a SD card to be used. To install the configuration file:

1. On a PC, insert a SD card into a card reader/writer in the PC, create a subdirectory called “transfer” on the SD card, and copy the configuration file to the transfer directory on the SD card. NOTE: the configuration file name must end in “.config”.

2. Place the SD card into a powered off DashDAQ and then power it up.

3. From the DashDAQ Main Menu, tap on [Setup], then tap on [Memory Card], then tap on [Install], then tap on [Config File].

4. The configuration file should be shown on the Install screen. Highlight the confuration file by tapping on it and tap OK. A popup should indicate the file was installed successfully. Tap OK on the popup.

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