Step 5: Press AC Filter and choose the filter for the measurement. The instrument uses three different AC filters that enable you either to optimize low frequency accuracy or to achieve faster AC settling times following a change in input signal amplitude. The three filters are 3 Hz, 20 Hz, and 200 Hz, and you should generally select the highest frequency filter whose frequency is less than that of the signal you are measuring, because higher frequency filters result in faster measurements. For example, when measuring a signal between 20 and 200 Hz, use the 20 Hz filter. If measurement speed is not an issue, choosing a lower frequency filter may result in quieter measurements, depending on the signal that you are measuring.
NOTE For accurate displayed statistics of AC measurements in Front Panel mode, the default manual trigger delay ( > Delay Man) must be used.
Resistance This section describes how to configure 2-wire and 4-wire resistance measurements from the front panel. Step 1: Configure the test leads as shown. 2-wire Resistance:
4-wire Resistance:
Step 2: Press [Ω2W] or [Ω4W] on the front panel. The following menu appears. (The Ω4W menu does not include Auto Zero.)
Step 3: The Aperture NPLC softkey is selected by default. Use the up/down arrow keys to specify integration time in power-line cycles (PLCs) to use for the measurement. 1, 10, and 100 PLC provide normal mode (line frequency noise) rejection. Selecting 100 PLC provides the best noise rejection and resolution, but the slowest measurements.
Step 4: Press Range to select a range for the measurement. (Auto (autorange) automatically selects the range for the measurement based on the input. Autoranging is convenient, but it results in slower measurements than using a manual range. Autoranging goes up a range at 120% of the present range, and down a range below 10% of the present range.
Press More to switch between the two pages of settings.
Notice the amount of test current sourced is shown for each range. After selecting a range, the main resistance menu is displayed.
Step 5: Auto Zero: Autozero provides the most accurate measurements, but requires additional time to perform the zero measurement.With autozero enabled (On), the DMM internally measures the offset following each measurement. It then subtracts that measurement from the preceding reading. This prevents offset voltages present on the DMM’s input circuitry from affecting measurement accuracy. With autozero disabled (Off), the DMM measures the offset once and subtracts the offset from all subsequent meaurements. The DMM takes a new offset measurement each time you change the function, range, or integration time. ( There is no autozero setting for 4-wire measurements.)
Negative Resistance Measurements Under certain conditions, the instrument may report negative resistance measurements. These may occur in 2-wire and 4-wire resistance measurements or continuity measurements. Conditions that may cause negative ohms values include: l Changes in Front/Rear switch contact resistance l Reversed Sense Hi and Lo leads l Circuits with external bias or thermal voltages at circuit connections l Changes in measurement connection after a NULL operation Under the same conditions, the DMM returns the measurement’s absolute value so as to prevent confusion associated with negative readings. The Hantek HDM Series DMMs will return negative values. This allows the most accurate results after a NULL operation.
Temperature This section describes how to configure 2-wire and 4-wire temperature measurements from the front panel. Temperature measurements require a temperature transducer probe. The supported probes are 2-wire and 4-wire RTDs, 2-wire and 4-wire thermistors. Step 1: Configure the test leads as shown. 2-wire Temperature:
4-wire Temperature:
Step 2: Press on the front panel. The following menu appears.