Starting with Hall effect sensor
The measured current has to flow through the package to produce any result.

Therefore, you have to cut the wire, and solder one end to one of the terminals, and the other end to the other terminal.

The nominal output is 1/2 Vcc, assuming you are using the birirectional variant. The datasheet states: 

 Datasheet, page 15


  Quiescent output voltage (VIOUT(Q)). The output of the device  when
  the primary current is zero. For bidirectional devices,  it nominally
  remains at VCC ⁄ 2.  Thus, VCC = 5 V translates  into VIOUT(QBI) = 2.5
  V. For unidirectional devices, it nomi- nally remains at 0.1 × VCC. 
  Thus, VCC = 5 V translates into  VIOUT(QUNI) = 0.5 V.  Variation in
  VIOUT(Q) can be attributed to  the resolution of the Allegro linear IC
  quiescent voltage trim,  magnetic hysteresis, and thermal drift.


QUNI means Quiescent (e.g. no current flow), unidirectional variant. QBI means Quiescent, Bi-Directional variant. VIOUT is the name of the output pin. See the pinout on page 1. 

Since you say you are getting ~1.6V, I would guess you're using the bidirectional variant, and powering it from 3.3V.



I don't know how you're having trouble figuring out the current, it's very simple:

 Datasheet, page 15


  Sensitivity (Sens). The change in device output in response to a  1 A
  change through the primary conductor. The sensitivity is the  product
  of the magnetic circuit sensitivity (G / A) and the linear  IC
  amplifier gain (mV/G). The linear IC amplifier gain is pro- grammed at
  the factory to optimize the sensitivity (mV/A) for the  half-scale
  current of the device.


There are multiple versions, with different sensitivity.

From page 2 of the datasheet:


The sensitivity is given in mV/A. Therefore, with a device with a 40mV/A sensitivity, 1A of current through the device will result in the output voltage increasing by 40mV.

The overall equation is:

$$V_{IOUT} = ( Vcc * OffsetScaling ) + ( Scaling Factor In Volts * Amps ) $$

\$OffsetScaling\$:


Bidirectional version = 0.5
Unidirectional version = 0.1


\$Scaling Factor In Volts\$:


This is the scaling factor given in the above table, converted to volts.


Therefore, for the bi-directional variant, with 40mv/A sensitivity, the output voltage will be:
$$V_{IOUT} = Vcc*0.5+ 0.040 * A$$
The uni-directional variant with 40mv/A sensitivity would be:
$$V_{IOUT} = Vcc* 0.1 + 0.040 * A$$

0.040 is 40mV in Volts. Change to match your device sensitivity.