AML is the only manufacturer of  Sensor-Xchangeable oceanographic instruments.  These instruments - the X•Series - allow the user to change any instrument's sensor-load, in the field and on demand.

Using the X•Series with Xchange^TM field-swappable sensors, your CTD can become an SVTP; Shallow pressure sensors can be swapped for deep; and temperature range can be extended or tightened, as needed.  In the example at left, a Smart•X real-time instrument - frequently used for AUV or ROV deployments - can be configured as a CTD, an SVP, a CT, or an SVTP.  Pressure range can vary - on demand - from 50 dBar to 6000 dBar and temperature range can switch between -2 to 32^oC and -2 to 45^oC or even 2 to 65^oC.  What to learn more?  Read about the benefits of Sensor Xchangeable instruments...

AML CTD's all offer 25Hz sampling; that is, the instruments sample as many as 25 times per second. High speed sampling ensure that there are sufficient data points to precisely identify thermoclines, picnoclines, or other changes in water conditions. The combination of sampling rate and desired spatial resolution
(vertical or horizontal) govern the travel speed of the instrument, which in turn impacts the total time requirement per deployment. Faster vertical profiles are possible with higher sampling rates.  For example:

• On an instrument travelling at a speed of 3 metres per second with a sampling rate of once per second, best guess estimates at thermoclines / picnoclines will be 3 meters;


• On an instrument travelling at a speed of 3 metres per second with a sampling rate of 25 samples per second, estimates of the boundaries of the same thermocline / picnocline to within 12cm.

With response times of 100ms (temperature), 10ms (pressure), and 25ms (conductivity), AML sensors quickly register minute changes in water conditions.  Errors due to sensor response time are a problem in rapidly changing water conditions. Such conditions occur with vertical profiling deployments, towed sensors,  sensors plumbed in on moving ships, and for moored instruments where internal waves are present in the water.   Any time an instrument is moored at the same depth as a picnocline the user should expect to see data oscillations due to internal waves.  

There are two effects associated with sensor response time errors.  The first is the effect on the accuracy of the measured sensor as a result of response time delays.  By far more significant, the second is the effect on the accuracy of the calculated parameters as a result of the mismatch between sensor response times.

Mismatches in sensor response times (primarily between C & T) cause anomalous errors in the salinity data.  These errors are typically referred to as salinity spikes.  Since salinity, temperature and pressure are used to calculate density and sound speed these data spikes also occur in those data sets.  The greater the mismatch in sensor response times between sensors, the larger the salinity spikes will be.  The salinity spike magnitude is also proportional to the thermal and conductivity gradients and the profiling speed.

Some manufacturers - for example SeaBird - have chosen to use pumps on their CTD instrumentation.   AML makes no use of pumps, resulting in two key benefits:

• AML instruments consume less power, an important constraint on autonomous vehicles such as gliders; and
• AML CTD data does not need to be 'smoothed' or 'corrected' to eliminate the effect of sensor data that is not time matched, a natural consequence of the use of a pump.